ultrabithorax

The Ubx gene contains a 5' exon, two micro-exons, an optional B element, and a C terminal exon. The Ubx genomic DNA length is 76 kb and its cDNA clone length is 3.2 to 4.6 kb. The 5' exon contains the 5'UTR which has 964 bases. The C terminal exon contains the 3'UTR which has 1580 to 2212 bases.

Ubx targets hundreds of different genes at different stages of morphogenesis including regulatory genes such as transcription factors, signalling components and terminal differentiation genes.{{cite journal | vauthors = Pavlopoulos A, Akam M | title = Hox gene Ultrabithorax regulates distinct sets of target genes at successive stages of Drosophila haltere morphogenesis | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 108 | issue = 7 | pages = 2855–2860 | date = February 2011 | pmid = 21282633 | pmc = 3041078 | doi = 10.1073/pnas.1015077108 | doi-access = free | bibcode = 2011PNAS..108.2855P }} Ubx has been shown to act upon long-range signaling molecules, as well as their target genes and subsequent genes further downstream. It has been shown to act at many levels of regulatory hierarchies, meaning Ubx can be used as a signal more than once in the same regulatory hierarchy.

Ubx represses selected Dpp (Decapentaplegic-activated) target genes in the anterior and posterior axis.{{cite journal | vauthors = Capovilla M, Brandt M, Botas J | title = Direct regulation of decapentaplegic by Ultrabithorax and its role in Drosophila midgut morphogenesis | journal = Cell | volume = 76 | issue = 3 | pages = 461–475 | date = February 1994 | pmid = 7906203 | doi = 10.1016/0092-8674(94)90111-2 | s2cid = 2281193 }} Several Dpp target genes which have been identified are spalt-related, vestigial, Serum Response Factor, and achaete-scute.{{cite journal | vauthors = Weatherbee SD, Halder G, Kim J, Hudson A, Carroll S | title = Ultrabithorax regulates genes at several levels of the wing-patterning hierarchy to shape the development of the Drosophila haltere | journal = Genes & Development | volume = 12 | issue = 10 | pages = 1474–1482 | date = May 1998 | pmid = 9585507 | pmc = 316835 | doi = 10.1101/gad.12.10.1474 }} Ubx also represses Wingless in the posterior compartment of the dorsoventral axis. The products of these genes are used in the regulation of morphological features between the wing and the haltere.

Ubx also selectively represses one enhancer of the vestigial genes in the proximodistal axis.

This gene is important for the development of hindwings in Lepidoptera, and leg development in larvae.{{cite journal | vauthors = Tendolkar A, Pomerantz AF, Heryanto C, Shirk PD, Patel NH, Martin A |title=Ultrabithorax Is a Micromanager of Hindwing Identity in Butterflies and Moths |journal=Frontiers in Ecology and Evolution |date= March 2021 |volume=9 |doi=10.3389/fevo.2021.643661 |issn=2296-701X|doi-access=free }}

Ubx is activated when there is a certain lack of Hunchback (hb) protein. Significant concentrations of Hunchback only exist in the anterior and posterior regions of the embryo, therefore Ubx is expressed only in middle segments. Thus, the hb gene may play an important role in the specification of the boundaries of Ubx expression.{{cite journal | vauthors = White RA, Lehmann R | title = A gap gene, hunchback, regulates the spatial expression of Ultrabithorax | journal = Cell | volume = 47 | issue = 2 | pages = 311–321 | date = October 1986 | pmid = 2876779 | doi = 10.1016/0092-8674(86)90453-8 | s2cid = 21253378 }}

Activation of Ubx involves multiple cis-acting regulatory sequences, which are found upstream and downstream of the mRNA cap-site. These enhancer regions can activate transcription of Ubx if the right combination of factors is present. For example, it has been shown that Ubx expression in the third femur of D. melanogaster is dependent on the enhancer regions abx and pbx.{{cite journal | vauthors = Davis GK, Srinivasan DG, Wittkopp PJ, Stern DL | title = The function and regulation of Ultrabithorax in the legs of Drosophila melanogaster | journal = Developmental Biology | volume = 308 | issue = 2 | pages = 621–631 | date = August 2007 | pmid = 17640629 | pmc = 2040266 | doi = 10.1016/j.ydbio.2007.06.002 }} Transcription factors which bind to the promoter site of Ubx have been purified and shown to activate expression of the gene in vitro.{{cite journal | vauthors = Biggin MD, Tjian R | title = Transcription factors that activate the Ultrabithorax promoter in developmentally staged extracts | journal = Cell | volume = 53 | issue = 5 | pages = 699–711 | date = June 1988 | pmid = 2897243 | doi = 10.1016/0092-8674(88)90088-8 | s2cid = 12199042 }}

Expression of Ubx is repressed by the long non-coding RNA Bithoraxoid (Bxd), using transcriptional interference to silence expression.{{cite journal | vauthors = Petruk S, Sedkov Y, Riley KM, Hodgson J, Schweisguth F, Hirose S, Jaynes JB, Brock HW, Mazo A | display-authors = 6 | title = Transcription of bxd noncoding RNAs promoted by trithorax represses Ubx in cis by transcriptional interference | journal = Cell | volume = 127 | issue = 6 | pages = 1209–1221 | date = December 2006 | pmid = 17174895 | pmc = 1866366 | doi = 10.1016/j.cell.2006.10.039 }}{{cite journal | vauthors = Petruk S, Sedkov Y, Brock HW, Mazo A | title = A model for initiation of mosaic HOX gene expression patterns by non-coding RNAs in early embryos | journal = RNA Biology | volume = 4 | issue = 1 | pages = 1–6 | year = 2007 | pmid = 17568198 | doi = 10.4161/rna.4.1.4300 | doi-access = free }}

Besides being a well known transcription factor, Ubx has been used to form biomaterials in vitro. Macroscale materials in the form of ropes, films and sheets can be generated from recombinant Ubx protein, which can self-assemble under gentler conditions than other biomaterial proteins.{{cite journal | vauthors = Greer AM, Huang Z, Oriakhi A, Lu Y, Lou J, Matthews KS, Bondos SE | title = The Drosophila transcription factor ultrabithorax self-assembles into protein-based biomaterials with multiple morphologies | journal = Biomacromolecules | volume = 10 | issue = 4 | pages = 829–837 | date = April 2009 | pmid = 19296655 | doi = 10.1021/bm801315v }} The macroscale materials self-adhere, allowing them to assume more complex structures. In addition to requiring less harsh conditions than other proteins, Ubx has been shown to assemble more rapidly and at much lower concentrations.

Ubx materials are mechanically robust. By altering fiber diameter, the breaking strength, breaking strain, and Young’s modulus can be tuned to values spanning an order of magnitude, ultimately changing the mechanism of extension.{{cite journal | vauthors = Huang Z, Lu Y, Majithia R, Shah J, Meissner K, Matthews KS, Bondos SE, Lou J | display-authors = 6 | title = Size dictates mechanical properties for protein fibers self-assembled by the Drosophila hox transcription factor ultrabithorax | journal = Biomacromolecules | volume = 11 | issue = 12 | pages = 3644–3651 | date = December 2010 | pmid = 21047055 | doi = 10.1021/bm1010992 }}

{{reflist}}

• [http://www.sdbonline.org/fly/segment/ultrabt1.htm Drosophila Ultrabithorax - The Interactive Fly]
• [https://www.google.co.uk/search?q=ultrabithorax+drosophila&source=lnms&tbm=isch&sa=X&ei=XBgcU4XpHIuThgekj4HwBA&ved=0CAcQ_AUoAQ&biw=1920&bih=973 Google search for images]

Category:Drosophila melanogaster genes

Category:Transcription factors

Category:Homeobox genes