Читать книгу Snyder and Champness Molecular Genetics of Bacteria - Tina M. Henkin - Страница 151

Once the RNA polymerase has initiated transcription at a promoter, it continues along the DNA, polymerizing ribonucleotides into a growing RNA chain, until it encounters a transcription termination signal. These termination sites are not necessarily at the ends of each individual gene. In bacteria, more than one gene is often transcribed into a single RNA, so a transcription termination site does not occur until the end of the cluster of genes that are transcribed together. Even if only a single gene is being transcribed, the transcription termination site may occur far downstream of the protein-coding region of the gene.

Bacterial RNA polymerase responds to two basic types of transcription termination signals, designated factor-independent (or intrinsic) and factor-dependent terminators (see Washburn and Gottesman, Suggested Reading). As their names imply, these types are distinguished by whether they work with just RNA polymerase and DNA alone or need other factors before they can terminate transcription. Both types of termination signal require participation of the newly transcribed RNA to promote termination, which means that RNA polymerase must transcribe the terminator region before termination can occur.