ctRNA

{{lowercase}}

{{Infobox rfam

| Name = ctRNA

| image = RF00489.jpg

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| caption = Predicted secondary structure and sequence conservation of ctRNA_p42d

| Symbol = ctRNA_p42d

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| Rfam = RF00489

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| RNA_type = Gene; antisense

| Tax_domain = Bacteria

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| SO = {{SO|0000644}}

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}}

In molecular biology ctRNA (counter-transcribed RNA) is a plasmid encoded noncoding RNA that binds to the mRNA of {{chem name|repB}} and causes translational inhibition.{{cite journal | last = Venkova-Canova | first = T |author2=Patek M |author3=Nesvera J | year = 2003 | title = Control of rep gene expression in plasmid pGA1 from Corynebacterium glutamicum | journal = J Bacteriol | volume = 185 | pages = 2402–2409 | pmid = 12670963 | doi = 10.1128/JB.185.8.2402-2409.2003 | issue = 8 | pmc = 152619}}

ctRNA is encoded by plasmids and functions in rolling circle replication to maintain a low copy number. In Corynebacterium glutamicum, it achieves this by antisense pairing with the mRNA of {{chem name|RepB}}, a replication initiation protein.

In Enterococcus faecium the plasmid pJB01 contains three open reading frames, copA, {{chem name|repB}}, and {{chem name|repC}}. The pJB01 ctRNA is coded on the opposite strand from the {{chem name|copA}}/{{chem name|repB}} intergenic region and partially overlaps an atypical ribosome binding site for {{chem name|repB}}.{{cite journal |vauthors=Kim SW, Jeong IS, Jeong EJ |title=The terminal and internal hairpin loops of the ctRNA of plasmid pJB01 play critical roles in regulating copy number |journal=Mol. Cells |volume=26 |issue=1 |pages=26–33 |date=July 2008 |pmid=18511887 |display-authors=etal}}