cotranscribed

Cotranscribed is an adjective used in genetics and molecular biology to describe transcripts that are produced during transcription or as part of the same transcriptional unit as another gene. In prokaryotes, cotranscription commonly refers to genes located in an operon that are transcribed together into a single polycistronic mRNA under the control of a shared promoter and terminator. Such transcripts allow coordinated expression of functionally related proteins. When operons are active, the products encoded by the cotranscribed genes are often translated from the same mRNA.

Classic examples include the lac operon in Escherichia coli (lacZ, lacY, lacA), and many other bacterial operons involved in metabolism and transport. In these cases, the cotranscribed genes are expressed in a coordinated manner, and regulatory elements influence all of them simultaneously.

In eukaryotes, cotranscription can describe events where RNA processing occurs concomitantly with transcription, a phenomenon known as cotranscriptional processing. Although most eukaryotic mRNAs are monocistronic, some genes produce polycistronic primary transcripts, such as clusters of microRNAs or small nucleolar RNAs that are processed from a single primary transcript.

The term cotranscribed is distinct from post-transcriptional processing and from transcription of separate transcripts; it emphasizes that multiple gene products share a transcriptional unit or are processed during transcription. Related concepts include operons, polycistronic transcripts, monocistronic transcription, and cotranscriptional processing.