Читать книгу Snyder and Champness Molecular Genetics of Bacteria - Tina M. Henkin - Страница 163

Different classes of RNAs have very different survival times in the cell. Highly structured RNAs, like rRNAs and tRNAs, are very stable and may persist through several rounds of cell division. Individual rRNAs are stabilized when they are assembled into ribosomal particles (see below), while tRNAs are stabilized because they are generally present in a complex with their cognate aaRS or with translation elongation factor Tu (EF-Tu) (see below). In contrast, most bacterial mRNAs are very unstable, with an average half-life in E. coli of 1 to 3 minutes; this term refers to the time required for the amount of an RNA to decrease to 50% of its initial level. The short half-life of mRNAs in bacteria contrasts with the situation in eukaryotes, where mRNAs are often very stable (with a half-life of hours). Efficient mRNA degradation is important for gene regulation and also releases nucleotides for use in new rounds of transcription. A variety of RNases participate in mRNA degradation, and the profiles of RNases vary somewhat in different groups of bacteria.