RNA activation

The phenomenon of RNAa was first reported in 2006 by Long-Cheng Li and colleagues at University of California, San Francisco (UCSF). They demonstrated that synthetic dsRNAs, termed saRNAs, could target gene promoters and induce potent and sustained upregulation of gene expression in human cells. This discovery challenged the prevailing view of small RNAs as solely negative regulators of gene expression. The Li group coined the term "small activating RNA" (saRNA) to distinguish these RNAs from those that mediate gene silencing.

Shortly after, in 2007, Janowski et al. independently confirmed RNAa, showing that dsRNAs could activate the expression of the progesterone receptor gene.{{cite journal |last1=Janowski |first1=BA |last2=Younger |first2=ST |last3=Hardy |first3=DB |last4=Ram |first4=R |last5=Huffman |first5=KE |last6=Corey |first6=DR |title=Activating gene expression in mammalian cells with promoter-targeted duplex RNAs. |journal=Nature Chemical Biology |date=March 2007 |volume=3 |issue=3 |pages=166–73 |doi=10.1038/nchembio860 |pmid=17259978}} Subsequent research revealed that endogenous miRNAs, traditionally known for gene silencing, could also activate gene expression through a process termed miRNA-mediated RNAa (mi-RNAa).{{cite journal |last1=Place |first1=RF |last2=Li |first2=LC |last3=Pookot |first3=D |last4=Noonan |first4=EJ |last5=Dahiya |first5=R |title=MicroRNA-373 induces expression of genes with complementary promoter sequences. |journal=Proceedings of the National Academy of Sciences of the United States of America |date=5 February 2008 |volume=105 |issue=5 |pages=1608–13 |doi=10.1073/pnas.0707594105 |doi-access=free |pmid=18227514|pmc=2234192 |bibcode=2008PNAS..105.1608P }}{{Erratum|doi=10.1073/pnas.1803343115|pmid=29555737|http://retractionwatch.com/2018/03/20/ucsf-va-investigation-finds-misconduct-in-highly-cited-pnas-paper/ Retraction Watch|https://retractionwatch.com/2022/12/08/professor-emeritus-loses-fourth-paper-after-ucsf-va-investigation-five-years-after-other-retractions/ Retraction Watch|checked=yes}}{{cite journal |last1=Huang |first1=V |last2=Place |first2=RF |last3=Portnoy |first3=V |last4=Wang |first4=J |last5=Qi |first5=Z |last6=Jia |first6=Z |last7=Yu |first7=A |last8=Shuman |first8=M |last9=Yu |first9=J |last10=Li |first10=LC |title=Upregulation of Cyclin B1 by miRNA and its implications in cancer. |journal=Nucleic Acids Research |date=February 2012 |volume=40 |issue=4 |pages=1695–707 |doi=10.1093/nar/gkr934 |pmid=22053081|pmc=3287204 }} Since the initial discovery of RNAa in human cells, many other groups have made similar observations in different mammalian species including human, non-human primates, rat and mice,{{cite journal |last1=Turunen |first1=MP |last2=Lehtola |first2=T |last3=Heinonen |first3=SE |last4=Assefa |first4=GS |last5=Korpisalo |first5=P |last6=Girnary |first6=R |last7=Glass |first7=CK |last8=Väisänen |first8=S |last9=Ylä-Herttuala |first9=S |title=Efficient regulation of VEGF expression by promoter-targeted lentiviral shRNAs based on epigenetic mechanism: a novel example of epigenetherapy. |journal=Circulation Research |date=11 September 2009 |volume=105 |issue=6 |pages=604–9 |doi=10.1161/CIRCRESAHA.109.200774 |pmid=19696410}}{{cite journal |last1=Huang |first1=V |last2=Qin |first2=Y |last3=Wang |first3=J |last4=Wang |first4=X |last5=Place |first5=RF |last6=Lin |first6=G |last7=Lue |first7=TF |last8=Li |first8=LC |title=RNAa is conserved in mammalian cells. |journal=PLOS ONE |date=22 January 2010 |volume=5 |issue=1 |pages=e8848 |doi=10.1371/journal.pone.0008848 |doi-access=free |pmid=20107511|pmc=2809750 |bibcode=2010PLoSO...5.8848H }}{{cite journal |last1=Matsui |first1=M |last2=Sakurai |first2=F |last3=Elbashir |first3=S |last4=Foster |first4=DJ |last5=Manoharan |first5=M |last6=Corey |first6=DR |title=Activation of LDL receptor expression by small RNAs complementary to a noncoding transcript that overlaps the LDLR promoter. |journal=Chemistry & Biology |date=22 December 2010 |volume=17 |issue=12 |pages=1344–55 |doi=10.1016/j.chembiol.2010.10.009 |pmid=21168770|pmc=3071588 }} plant {{cite journal |last1=Shibuya |first1=K |last2=Fukushima |first2=S |last3=Takatsuji |first3=H |title=RNA-directed DNA methylation induces transcriptional activation in plants. |journal=Proceedings of the National Academy of Sciences of the United States of America |date=3 February 2009 |volume=106 |issue=5 |pages=1660–5 |doi=10.1073/pnas.0809294106 |doi-access=free |pmid=19164525|pmc=2629447 |bibcode=2009PNAS..106.1660S }} and C. elegans.{{cite journal |last1=Seth |first1=M |last2=Shirayama |first2=M |last3=Gu |first3=W |last4=Ishidate |first4=T |last5=Conte D |first5=Jr |last6=Mello |first6=CC |title=The C. elegans CSR-1 argonaute pathway counteracts epigenetic silencing to promote germline gene expression. |journal=Developmental Cell |date=23 December 2013 |volume=27 |issue=6 |pages=656–63 |doi=10.1016/j.devcel.2013.11.014 |pmid=24360782|pmc=3954781 }}{{cite journal |last1=Turner |first1=MJ |last2=Jiao |first2=AL |last3=Slack |first3=FJ |title=Autoregulation of lin-4 microRNA transcription by RNA activation (RNAa) in C. elegans. |journal=Cell Cycle |date=2014 |volume=13 |issue=5 |pages=772–81 |doi=10.4161/cc.27679 |pmid=24398561|pmc=3979913 }}

The molecular mechanism of RNAa is not fully understood. Similar to RNAi, it has been shown that

mammalian RNAa requires members of the Ago clade of Argonaute proteins, particularly Ago2,

name="li_pnas" />{{cite journal |last1=Chu |first1=Y |last2=Yue |first2=X |last3=Younger |first3=ST |last4=Janowski |first4=BA |last5=Corey |first5=DR |title=Involvement of argonaute proteins in gene silencing and activation by RNAs complementary to a non-coding transcript at the progesterone receptor promoter. |journal=Nucleic Acids Research |date=November 2010 |volume=38 |issue=21 |pages=7736–48 |doi=10.1093/nar/gkq648 |pmid=20675357|pmc=2995069 }}{{cite journal |last1=Meng |first1=X |last2=Jiang |first2=Q |last3=Chang |first3=N |last4=Wang |first4=X |last5=Liu |first5=C |last6=Xiong |first6=J |last7=Cao |first7=H |last8=Liang |first8=Z |title=Small activating RNA binds to the genomic target site in a seed-region-dependent manner. |journal=Nucleic Acids Research |date=18 March 2016 |volume=44 |issue=5 |pages=2274–82 |doi=10.1093/nar/gkw076 |pmid=26873922|pmc=4797303 }} but possesses kinetics distinct from RNAi, characterized by a delayed

onset and sustained activity over multiple cell divisions.{{cite book |chapter-url=https://books.google.com/books?id=r67Lrf9r9XEC&pg=PA189 |

last=Li |first=Long-Cheng |chapter=Small RNA-mediated gene activation |editor1-first=Kevin V |editor1-last=Morris |title=RNA and the Regulation of Gene Expression: A Hidden Layer of Complexity |date=2008 |publisher=Caister Academic Press |location=Norfolk, U.K |isbn=978-1-904455-25-7 |pages=189–99}}{{cite journal |last1=Place |first1=RF |last2=Noonan |first2=EJ |last3=Földes-Papp |first3=Z |last4=Li |first4=LC |title=Defining features and exploring chemical modifications to manipulate RNAa activity. |journal=Current Pharmaceutical Biotechnology |date=August 2010 |volume=11 |issue=5 |pages=518–26 |doi=10.2174/138920110791591463 |pmid=20662764|pmc=3413318 }}{{cite journal |last1=Portnoy |first1=V |last2=Huang |first2=V |last3=Place |first3=RF |last4=Li |first4=LC |title=Small RNA and transcriptional upregulation. |journal=Wiley Interdisciplinary Reviews. RNA |date=September 2011 |volume=2 |issue=5 |pages=748–60 |doi=10.1002/wrna.90 |pmid=21823233|pmc=3154074 }} In contrast to RNAi, promoter-targeted saRNAs induce prolonged activation of gene expression associated with epigenetic

changes.

The mechanism of saRNA-mediated RNAa centers around the RNA-induced transcriptional activation (RITA) complex.{{cite journal |last1=Portnoy |first1=V |last2=Lin |first2=SH |last3=Li |first3=KH |last4=Burlingame |first4=A |last5=Hu |first5=ZH |last6=Li |first6=H |last7=Li |first7=LC |title=saRNA-guided Ago2 targets the RITA complex to promoters to stimulate transcription. |journal=Cell Research |date=March 2016 |volume=26 |issue=3 |pages=320–35 |doi=10.1038/cr.2016.22 |pmid=26902284|pmc=4783471 }} This complex includes:

• Argonaute 2 (AGO2): AGO2 binds to the guide strand of the saRNA and facilitates targeting to the gene promoter. AGO2 is the primary Argonaute protein involved in saRNA-mediated RNAa.
• RNA Helicase A (RHA): RHA is thought to unwind the DNA helix, allowing the saRNA to bind to its target sequence.
• CTR9 (Component of the PAF1 Complex): CTR9, a key part of the PAF1 complex (PAF1C), is recruited to the promoter.{{cite journal |last1=Zhao |first1=X |last2=Reebye |first2=V |last3=Hitchen |first3=P |last4=Fan |first4=J |last5=Jiang |first5=H |last6=Sætrom |first6=P |last7=Rossi |first7=J |last8=Habib |first8=NA |last9=Huang |first9=KW |title=Mechanisms involved in the activation of C/EBPα by small activating RNA in hepatocellular carcinoma. |journal=Oncogene |date=May 2019 |volume=38 |issue=18 |pages=3446–3457 |doi=10.1038/s41388-018-0665-6 |pmid=30643190}}{{cite journal |last1=Voutila |first1=J |last2=Reebye |first2=V |last3=Roberts |first3=TC |last4=Protopapa |first4=P |last5=Andrikakou |first5=P |last6=Blakey |first6=DC |last7=Habib |first7=R |last8=Huber |first8=H |last9=Saetrom |first9=P |last10=Rossi |first10=JJ |last11=Habib |first11=NA |title=Development and Mechanism of Small Activating RNA Targeting CEBPA, a Novel Therapeutic in Clinical Trials for Liver Cancer. |journal=Molecular Therapy |date=6 December 2017 |volume=25 |issue=12 |pages=2705–2714 |doi=10.1016/j.ymthe.2017.07.018 |pmid=28882451|pmc=5768526 }} PAF1C plays a crucial role in regulating RNA Polymerase II (RNAP II) activity.{{cite journal |last1=Xie |first1=Y |last2=Zheng |first2=M |last3=Chu |first3=X |last4=Chen |first4=Y |last5=Xu |first5=H |last6=Wang |first6=J |last7=Zhou |first7=H |last8=Long |first8=J |title=Paf1 and Ctr9 subcomplex formation is essential for Paf1 complex assembly and functional regulation. |journal=Nature Communications |date=18 September 2018 |volume=9 |issue=1 |pages=3795 |doi=10.1038/s41467-018-06237-7 |pmid=30228257|pmc=6143631 |bibcode=2018NatCo...9.3795X }}{{cite journal |last1=Francette |first1=AM |last2=Tripplehorn |first2=SA |last3=Arndt |first3=KM |title=The Paf1 Complex: A Keystone of Nuclear Regulation Operating at the Interface of Transcription and Chromatin. |journal=Journal of Molecular Biology |date=9 July 2021 |volume=433 |issue=14 |pages=166979 |doi=10.1016/j.jmb.2021.166979 |pmid=33811920|pmc=8184591 }}

The RITA complex assembly at the target gene promoter leads to a shift in the transcriptional machinery, promoting the transition from paused to elongating RNAP II. This is evidenced by changes in phosphorylation patterns at the transcriptional start site (TSS): a decrease in Ser5-phosphorylated RNAP II (pausing) and an increase in Ser2-phosphorylated RNAP II (elongating). Histone H2B monoubiquitination is also an early epigenetic event associated with RNAa, promoting further histone modifications that enhance active transcription.

Endogenous miRNAs, typically known for their role in post-transcriptional gene silencing, can also activate gene expression. The mechanisms of mi-RNAa are diverse. Several models have been proposed:

• Release of Paused RNAP II: miR-34a, for example, has been shown to bind to a long non-coding RNA (lncRNA) transcribed from the ZMYND10 promoter. This interaction recruits the RNA-induced silencing complex (RISC), which then forms a complex with DDX21 and CDK9 (components of the positive transcription elongation factor b, P-TEFb). This complex facilitates the release of paused RNAP II at the promoter, allowing for active transcription.{{cite journal |last1=Ohno |first1=SI |last2=Oikawa |first2=K |last3=Tsurui |first3=T |last4=Harada |first4=Y |last5=Ono |first5=K |last6=Tateishi |first6=M |last7=Mirza |first7=A |last8=Takanashi |first8=M |last9=Kanekura |first9=K |last10=Nagase |first10=K |last11=Shimada |first11=Y |last12=Kudo |first12=Y |last13=Ikeda |first13=N |last14=Ochiya |first14=T |last15=Wang |first15=X |last16=Kuroda |first16=M |title=Nuclear microRNAs release paused Pol II via the DDX21-CDK9 complex. |journal=Cell Reports |date=12 April 2022 |volume=39 |issue=2 |pages=110673 |doi=10.1016/j.celrep.2022.110673 |pmid=35417682|doi-access=free }}
• TATA Box Targeting: Some miRNAs including those encoded by HIV-1 virus and human endogenous ones have been shown to directly target the TATA box motif in gene promoters to facilitate pre-initiation complexes (PICs) assembly and transcription initiation.{{cite journal |last1=Zhang |first1=Y |last2=Fan |first2=M |last3=Zhang |first3=X |last4=Huang |first4=F |last5=Wu |first5=K |last6=Zhang |first6=J |last7=Liu |first7=J |last8=Huang |first8=Z |last9=Luo |first9=H |last10=Tao |first10=L |last11=Zhang |first11=H |title=Cellular microRNAs up-regulate transcription via interaction with promoter TATA-box motifs. |journal=RNA |date=December 2014 |volume=20 |issue=12 |pages=1878–89 |doi=10.1261/rna.045633.114 |pmid=25336585|pmc=4238354 }}{{cite journal |last1=Xiao |first1=M |last2=Li |first2=J |last3=Li |first3=W |last4=Wang |first4=Y |last5=Wu |first5=F |last6=Xi |first6=Y |last7=Zhang |first7=L |last8=Ding |first8=C |last9=Luo |first9=H |last10=Li |first10=Y |last11=Peng |first11=L |last12=Zhao |first12=L |last13=Peng |first13=S |last14=Xiao |first14=Y |last15=Dong |first15=S |last16=Cao |first16=J |last17=Yu |first17=W |title=MicroRNAs activate gene transcription epigenetically as an enhancer trigger. |journal=RNA Biology |date=3 October 2017 |volume=14 |issue=10 |pages=1326–1334 |doi=10.1080/15476286.2015.1112487 |pmid=26853707|pmc=5711461 }}{{cite book |last1=Zou |first1=Q |last2=Liang |first2=Y |last3=Luo |first3=H |last4=Yu |first4=W |chapter=MiRNA-Mediated RNAa by Targeting Enhancers |title=RNA Activation |series=Advances in Experimental Medicine and Biology |date=2017 |volume=983 |pages=113–125 |doi=10.1007/978-981-10-4310-9_8 |pmid=28639195|isbn=978-981-10-4309-3 }}
• Targeting of RNA Transcripts: Some miRNAs can bind to RNA transcripts that overlap with the promoter.{{cite journal |last1=Luo |first1=J |last2=Ji |first2=Y |last3=Chen |first3=N |last4=Song |first4=G |last5=Zhou |first5=S |last6=Niu |first6=X |last7=Yu |first7=D |title=Nuclear miR-150 enhances hepatic lipid accumulation by targeting RNA transcripts overlapping the PLIN2 promoter. |journal=iScience |date=20 October 2023 |volume=26 |issue=10 |pages=107837 |doi=10.1016/j.isci.2023.107837 |pmid=37736048|pmc=10509351 |bibcode=2023iSci...26j7837L }}

• DNA Triplex Formation: miRNAs can directly bind double-stranded DNA (dsDNA) at purine-rich sequences, forming triple-helical structures that upregulate gene expression. This interaction, identified through biophysical methods and the computational algorithm Trident, suggests a novel mechanism of miRNA-mediated gene activation.{{cite journal |last1=Paugh |first1=SW |last2=Coss |first2=DR |last3=Bao |first3=J |last4=Laudermilk |first4=LT |last5=Grace |first5=CR |last6=Ferreira |first6=AM |last7=Waddell |first7=MB |last8=Ridout |first8=G |last9=Naeve |first9=D |last10=Leuze |first10=M |last11=LoCascio |first11=PF |last12=Panetta |first12=JC |last13=Wilkinson |first13=MR |last14=Pui |first14=CH |last15=Naeve |first15=CW |last16=Uberbacher |first16=EC |last17=Bonten |first17=EJ |last18=Evans |first18=WE |title=MicroRNAs Form Triplexes with Double Stranded DNA at Sequence-Specific Binding Sites; a Eukaryotic Mechanism via which microRNAs Could Directly Alter Gene Expression. |journal=PLOS Computational Biology |date=February 2016 |volume=12 |issue=2 |pages=e1004744 |doi=10.1371/journal.pcbi.1004744 |doi-access=free |pmid=26844769|bibcode=2016PLSCB..12E4744P }} Argonaute proteins may stabilize these miRNA-DNA triplexes.{{cite journal |last1=Toscano-Garibay |first1=JD |last2=Aquino-Jarquin |first2=G |title=Transcriptional regulation mechanism mediated by miRNA-DNA•DNA triplex structure stabilized by Argonaute. |journal=Biochimica et Biophysica Acta (BBA) - Gene Regulatory Mechanisms |date=November 2014 |volume=1839 |issue=11 |pages=1079–83 |doi=10.1016/j.bbagrm.2014.07.016 |pmid=25086339}}

A critical aspect of RNAa is the nuclear import of saRNAs and miRNAs. While the exact mechanisms are still under investigation, several pathways have been implicated:

• Importin-8: Importin-8 has been shown to mediate the nuclear import of mature miRNAs.{{cite journal |last1=Wei |first1=Y |last2=Li |first2=L |last3=Wang |first3=D |last4=Zhang |first4=CY |last5=Zen |first5=K |title=Importin 8 regulates the transport of mature microRNAs into the cell nucleus. |journal=The Journal of Biological Chemistry |date=11 April 2014 |volume=289 |issue=15 |pages=10270–10275 |doi=10.1074/jbc.C113.541417 |doi-access=free |pmid=24596094|pmc=4036152 }}
• AGO2-dependent transport: AGO2 itself may play a role in the nuclear localization of saRNAs.

RNAa has been observed in a wide range of organisms, suggesting its evolutionary conservation and fundamental biological importance. It has been documented in:

• Mammals: RNAa has been demonstrated in cells from humans, non-human primates, mice, and rats.
• C. elegans: In C. elegans, the Argonaute protein CSR-1, along with its 22G-RNA cofactors, is required for chromosome segregation and counteracts epigenetic silencing to promote gene expression.{{cite journal |last1=Conine |first1=CC |last2=Moresco |first2=JJ |last3=Gu |first3=W |last4=Shirayama |first4=M |last5=Conte D |first5=Jr |last6=Yates JR |first6=3rd |last7=Mello |first7=CC |title=Argonautes promote male fertility and provide a paternal memory of germline gene expression in C. elegans. |journal=Cell |date=19 December 2013 |volume=155 |issue=7 |pages=1532–44 |doi=10.1016/j.cell.2013.11.032 |pmid=24360276|pmc=3924572 }}{{cite journal |last1=Wedeles |first1=CJ |last2=Wu |first2=MZ |last3=Claycomb |first3=JM |title=Protection of germline gene expression by the C. elegans Argonaute CSR-1. |journal=Developmental Cell |date=23 December 2013 |volume=27 |issue=6 |pages=664–71 |doi=10.1016/j.devcel.2013.11.016 |pmid=24360783}}
• Plants: In plants, RNA-directed DNA methylation (RdDM) can induce transcriptional activation, creating heritable epialleles.
• Insects: RNAa has been demonstrated in insects, where it can be used to activate both endogenous and exogenous genes.{{cite journal |last1=De Hayr |first1=L |last2=Asad |first2=S |last3=Hussain |first3=M |last4=Asgari |first4=S |title=RNA activation in insects: The targeted activation of endogenous and exogenous genes. |journal=Insect Biochemistry and Molecular Biology |date=April 2020 |volume=119 |pages=103325 |doi=10.1016/j.ibmb.2020.103325 |pmid=31978586|bibcode=2020IBMB..11903325D }}
• Ticks: RNAa has been shown to regulate endochitinase genes in ticks.{{cite journal |last1=Kwofie |first1=Kofi Dadzie |last2=Hernandez |first2=Emmanuel Pacia |last3=Kawada |first3=Hayato |last4=Koike |first4=Yuki |last5=Sasaki |first5=Sana |last6=Inoue |first6=Takahiro |last7=Jimbo |first7=Kei |last8=Mikami |first8=Fusako |last9=Ladzekpo |first9=Danielle |last10=Umemiya-Shirafuji |first10=Rika |last11=Yamaji |first11=Kayoko |last12=Tanaka |first12=Tetsuya |last13=Matsubayashi |first13=Makoto |last14=Alim |first14=Md Abdul |last15=Dadzie |first15=Samuel Kweku |last16=Iwanaga |first16=Shiroh |last17=Tsuji |first17=Naotoshi |last18=Hatta |first18=Takeshi |title=RNA activation in ticks |journal=Scientific Reports |date=8 June 2023 |volume=13 |issue=1 |page=9341 |doi=10.1038/s41598-023-36523-4|pmid=37291173 |pmc=10250327 |bibcode=2023NatSR..13.9341K }}

RNAa has been used as a convenient tool by many scientists to study gene function in lieu of vector-based gene overexpression.{{cite journal |last1=Wang |first1=J |last2=Place |first2=RF |last3=Huang |first3=V |last4=Wang |first4=X |last5=Noonan |first5=EJ |last6=Magyar |first6=CE |last7=Huang |first7=J |last8=Li |first8=LC |title=Prognostic value and function of KLF4 in prostate cancer: RNAa and vector-mediated overexpression identify KLF4 as an inhibitor of tumor cell growth and migration. |journal=Cancer Research |date=15 December 2010 |volume=70 |issue=24 |pages=10182–91 |doi=10.1158/0008-5472.CAN-10-2414 |pmid=21159640|pmc=3076047 }}{{cite journal |last1=Chao |first1=G |last2=Wang |first2=Z |last3=Yang |first3=Y |last4=Zhang |first4=S |title=LncRNA H19 as a Competing Endogenous RNA to Regulate AQP Expression in the Intestinal Barrier of IBS-D Patients. |journal=Frontiers in Physiology |date=2020 |volume=11 |pages=602076 |doi=10.3389/fphys.2020.602076 |doi-access=free |pmid=33584332|pmc=7874183 }}{{cite journal |last1=Pineda |first1=RH |last2=Nedumaran |first2=B |last3=Hypolite |first3=J |last4=Pan |first4=XQ |last5=Wilson |first5=S |last6=Meacham |first6=RB |last7=Malykhina |first7=AP |title=Altered expression and modulation of the two-pore-domain (K(2P)) mechanogated potassium channel TREK-1 in overactive human detrusor. |journal=American Journal of Physiology. Renal Physiology |date=1 August 2017 |volume=313 |issue=2 |pages=F535–F546 |doi=10.1152/ajprenal.00638.2016 |pmid=28539337|pmc=6148548 }}

RNAa offers promising therapeutic potential because of its ability to increase gene expression. This provides a different approach for treating diseases caused by gene underexpression or loss-of-function mutations. saRNAs for a number of genes have been tested in various cell and animal disease models for therapeutic efficacy.{{cite journal |last1=Tan |first1=CP |last2=Sinigaglia |first2=L |last3=Gomez |first3=V |last4=Nicholls |first4=J |last5=Habib |first5=NA |title=RNA Activation-A Novel Approach to Therapeutically Upregulate Gene Transcription. |journal=Molecules |date=28 October 2021 |volume=26 |issue=21 |page=6530 |doi=10.3390/molecules26216530 |doi-access=free |pmid=34770939|pmc=8586927 }}

• Cancer: saRNAs have been used to reactivate tumor suppressor genes, inhibit cancer cell proliferation, and reduce tumor growth in animal models.Bi, C.Q., Kang, T., Qian, Y.K., et al. (2024). Upregulation of LHPP by saRNA inhibited hepatocellular cancer cell proliferation and xenograft tumor growth. PLoS One 19: e0299522.Wang, L., Lin, Y., Yao, Z., et al. (2024). Targeting undruggable phosphatase overcomes trastuzumab resistance by inhibiting multi-oncogenic kinases. Drug Resist Updat 76: 101118.{{cite journal |last1=Kang |first1=MR |last2=Yang |first2=G |last3=Place |first3=RF |last4=Charisse |first4=K |last5=Epstein-Barash |first5=H |last6=Manoharan |first6=M |last7=Li |first7=LC |title=Intravesical delivery of small activating RNA formulated into lipid nanoparticles inhibits orthotopic bladder tumor growth. |journal=Cancer Research |date=1 October 2012 |volume=72 |issue=19 |pages=5069–79 |doi=10.1158/0008-5472.CAN-12-1871 |pmid=22869584}}{{cite journal |last1=Yoon |first1=S |last2=Huang |first2=KW |last3=Reebye |first3=V |last4=Mintz |first4=P |last5=Tien |first5=YW |last6=Lai |first6=HS |last7=Sætrom |first7=P |last8=Reccia |first8=I |last9=Swiderski |first9=P |last10=Armstrong |first10=B |last11=Jozwiak |first11=A |last12=Spalding |first12=D |last13=Jiao |first13=L |last14=Habib |first14=N |last15=Rossi |first15=JJ |title=Targeted Delivery of C/EBPα -saRNA by Pancreatic Ductal Adenocarcinoma-specific RNA Aptamers Inhibits Tumor Growth In Vivo. |journal=Molecular Therapy |date=June 2016 |volume=24 |issue=6 |pages=1106–1116 |doi=10.1038/mt.2016.60 |pmid=26983359|pmc=4923325 }}{{cite journal |last1=Reebye |first1=V |last2=Huang |first2=KW |last3=Lin |first3=V |last4=Jarvis |first4=S |last5=Cutilas |first5=P |last6=Dorman |first6=S |last7=Ciriello |first7=S |last8=Andrikakou |first8=P |last9=Voutila |first9=J |last10=Saetrom |first10=P |last11=Mintz |first11=PJ |last12=Reccia |first12=I |last13=Rossi |first13=JJ |last14=Huber |first14=H |last15=Habib |first15=R |last16=Kostomitsopoulos |first16=N |last17=Blakey |first17=DC |last18=Habib |first18=NA |title=Gene activation of CEBPA using saRNA: preclinical studies of the first in human saRNA drug candidate for liver cancer. |journal=Oncogene |date=June 2018 |volume=37 |issue=24 |pages=3216–3228 |doi=10.1038/s41388-018-0126-2 |pmid=29511346|pmc=6013054 }}{{cite journal |last1=Su |first1=R |last2=Wen |first2=Z |last3=Zhan |first3=X |last4=Long |first4=Y |last5=Wang |first5=X |last6=Li |first6=C |last7=Su |first7=Y |last8=Fei |first8=J |title=Small RNA activation of CDH13 expression overcome BCR-ABL1-independent imatinib-resistance and their signaling pathway studies in chronic myeloid leukemia. |journal=Cell Death & Disease |date=23 August 2024 |volume=15 |issue=8 |pages=615 |doi=10.1038/s41419-024-07006-9 |pmid=39179585|pmc=11343752 }}
• Metabolic Disorders: saRNAs have been used to upregulate the expression of SIRT1, showing potential for reversing metabolic syndrome.{{cite journal |last1=Andrikakou |first1=P |last2=Reebye |first2=V |last3=Vasconcelos |first3=D |last4=Yoon |first4=S |last5=Voutila |first5=J |last6=George |first6=AJT |last7=Swiderski |first7=P |last8=Habib |first8=R |last9=Catley |first9=M |last10=Blakey |first10=D |last11=Habib |first11=NA |last12=Rossi |first12=JJ |last13=Huang |first13=KW |title=Enhancing SIRT1 Gene Expression Using Small Activating RNAs: A Novel Approach for Reversing Metabolic Syndrome. |journal=Nucleic Acid Therapeutics |date=December 2022 |volume=32 |issue=6 |pages=486–496 |doi=10.1089/nat.2021.0115 |pmid=35895511}}
• Cardiovascular Disorders: saRNAs targeting VEGFA gene in the form of shRNA have been tested for the treatment of peripheral artery disease and myocardial infarction.{{cite journal |last1=Turunen |first1=MP |last2=Husso |first2=T |last3=Musthafa |first3=H |last4=Laidinen |first4=S |last5=Dragneva |first5=G |last6=Laham-Karam |first6=N |last7=Honkanen |first7=S |last8=Paakinaho |first8=A |last9=Laakkonen |first9=JP |last10=Gao |first10=E |last11=Vihinen-Ranta |first11=M |last12=Liimatainen |first12=T |last13=Ylä-Herttuala |first13=S |title=Epigenetic upregulation of endogenous VEGF-A reduces myocardial infarct size in mice. |journal=PLOS ONE |date=2014 |volume=9 |issue=2 |pages=e89979 |doi=10.1371/journal.pone.0089979 |doi-access=free |pmid=24587164|pmc=3935957 |bibcode=2014PLoSO...989979T }} and erectile dysfunction (ED).{{cite journal |last1=Chen |first1=R |last2=Wang |first2=T |last3=Rao |first3=K |last4=Yang |first4=J |last5=Zhang |first5=S |last6=Wang |first6=S |last7=Liu |first7=J |last8=Ye |first8=Z |title=Up-regulation of VEGF by small activator RNA in human corpus cavernosum smooth muscle cells. |journal=The Journal of Sexual Medicine |date=October 2011 |volume=8 |issue=10 |pages=2773–80 |doi=10.1111/j.1743-6109.2011.02412.x |pmid=21819543}} saRNA-mediated activation of βII spectrin alleviated ischemia/reperfusion (I/R)-induced cardiac contractile dysfunction.{{cite journal |last1=Yang |first1=R |last2=Ruan |first2=B |last3=Wang |first3=R |last4=Zhang |first4=X |last5=Xing |first5=P |last6=Li |first6=C |last7=Zhang |first7=Y |last8=Chang |first8=X |last9=Song |first9=H |last10=Zhang |first10=S |last11=Zhao |first11=H |last12=Zhang |first12=F |last13=Yin |first13=T |last14=Qi |first14=T |last15=Yan |first15=W |last16=Zhang |first16=F |last17=Hu |first17=G |last18=Wang |first18=S |last19=Tao |first19=L |title=Cardiomyocyte βII spectrin plays a critical role in maintaining cardiac function by regulating mitochondrial respiratory function. |journal=Cardiovascular Research |date=21 September 2024 |volume=120 |issue=11 |pages=1312–1326 |doi=10.1093/cvr/cvae116 |pmid=38832923}}
• Neurodegenerative Disease: saRNAs targeting the BACE2 gene have been used to reduce Abeta production.{{cite journal |last1=Liu |first1=H |last2=Chen |first2=S |last3=Sun |first3=Q |last4=Sha |first4=Q |last5=Tang |first5=Y |last6=Jia |first6=W |last7=Chen |first7=L |last8=Zhao |first8=J |last9=Wang |first9=T |last10=Sun |first10=X |title=Let-7c increases BACE2 expression by RNAa and decreases Aβ production. |journal=American Journal of Translational Research |date=2022 |volume=14 |issue=2 |pages=899–908 |pmid=35273693|pmc=8902526 }}
• Other Therapeutic Applications: saRNAs have been tested in several other disease models, including acute lung injury (ALI)/acute respiratory distress syndrome (ARDS){{cite journal |last1=Zhang |first1=L |last2=Chen |first2=S |last3=Zheng |first3=Z |last4=Lin |first4=Y |last5=Wang |first5=C |last6=Gong |first6=Y |last7=Qin |first7=A |last8=Su |first8=J |last9=Tang |first9=S |title=Artificial Neutrophil-Mediated CEBPA-saRNA Delivery to Ameliorate ALI/ARDS. |journal=ACS Applied Materials & Interfaces |date=2 October 2024 |volume=16 |issue=39 |pages=51957–51969 |doi=10.1021/acsami.4c09022 |pmid=39305228}} and proliferative vitreoretinopathy (PVR).{{cite journal |last1=Zhang |first1=Q |last2=Guo |first2=Y |last3=Kang |first3=M |last4=Lin |first4=WH |last5=Wu |first5=JC |last6=Yu |first6=Y |last7=Li |first7=LC |last8=Sang |first8=A |title=p21CIP/WAF1 saRNA inhibits proliferative vitreoretinopathy in a rabbit model. |journal=PLOS ONE |date=2023 |volume=18 |issue=2 |pages=e0282063 |doi=10.1371/journal.pone.0282063 |doi-access=free |pmid=36821623|pmc=9949646 |bibcode=2023PLoSO..1882063Z }}

Several saRNA therapeutics have entered clinical trials:

• MTL-CEBPA: This saRNA targets the C/EBPα gene and is being evaluated for the treatment of advanced liver cancer. Early clinical trials showed that MTL-CEBPA was well-tolerated and demonstrated signs of clinical activity.{{cite journal |last1=Sarker |first1=D |last2=Plummer |first2=R |last3=Meyer |first3=T |last4=Sodergren |first4=MH |last5=Basu |first5=B |last6=Chee |first6=CE |last7=Huang |first7=KW |last8=Palmer |first8=DH |last9=Ma |first9=YT |last10=Evans |first10=TRJ |last11=Spalding |first11=DRC |last12=Pai |first12=M |last13=Sharma |first13=R |last14=Pinato |first14=DJ |last15=Spicer |first15=J |last16=Hunter |first16=S |last17=Kwatra |first17=V |last18=Nicholls |first18=JP |last19=Collin |first19=D |last20=Nutbrown |first20=R |last21=Glenny |first21=H |last22=Fairbairn |first22=S |last23=Reebye |first23=V |last24=Voutila |first24=J |last25=Dorman |first25=S |last26=Andrikakou |first26=P |last27=Lloyd |first27=P |last28=Felstead |first28=S |last29=Vasara |first29=J |last30=Habib |first30=R |last31=Wood |first31=C |last32=Saetrom |first32=P |last33=Huber |first33=HE |last34=Blakey |first34=DC |last35=Rossi |first35=JJ |last36=Habib |first36=N |title=MTL-CEBPA, a Small Activating RNA Therapeutic Upregulating C/EBP-α, in Patients with Advanced Liver Cancer: A First-in-Human, Multicenter, Open-Label, Phase I Trial. |journal=Clinical Cancer Research|date=1 August 2020 |volume=26 |issue=15 |pages=3936–3946 |doi=10.1158/1078-0432.CCR-20-0414 |pmid=32357963|url=https://discovery.ucl.ac.uk/id/eprint/10097721/1/Meyer_MTL-CEBPA%2C%20a%20small%20activating%20RNA%20therapeutic%20up-regulating%20C%3AEBP-%CE%B1_AAM.pdf }}

{{Reflist}}

• {{cite book |author=Li, Long-Cheng |title=RNA Activation |publisher=Springer Nature |year=2017 |isbn= 978-9811043093}}
• {{cite journal | vauthors = Check E | title = RNA interference: hitting the on switch | journal = Nature | volume = 448 | issue = 7156 | pages = 855–8 | date = August 2007| doi = 10.1038/448855a | pmid = 17713502 | bibcode = 2007Natur.448..855C }}

• [https://www.newscientist.com/channel/life/genetics/mg19225780.149-how-to-get-your-genes-switched-on.html How to get your genes switched on]

Category:RNA

Category:Gene expression

Category:Epigenetics