Wednesday, May 30, 2012

tssRNA , a new type of transcription start site associated small RNA in bacteria

Researchers from Spain have identified a  new class of small RNA (~45 bases long)  in gram positive and negative bacteria. These tssRNAs are associated with RNA polymerase pausing some 45 bases downstream of the transcription start site and show global changes in expression during the growth cycle.  They are related to eukaryotic tiRNAs in their localization (transcription start sites, TSS) but not in their biogenesis. tssRNAs are generated at the same positions
 as long transcripts, as well as at independent positions, but both seem to have promoter-like characteristics (Pribnow box).  They have shown  that RNA polymerase is halted at tssRNAs positions, both in bona fide genes and in positions where no long transcript is produced. These Researchers have  hypothesized  that the incorrect assembly of processive RNA polymerase complexes could lead to premature termination of RNA transcripts, which in turn could result in deleteriously truncated proteins. tssRNAs could be part of a regulatory mechanism that prevents transcription from starting before the correct RNA polymerase complex is assembled. It is still unclear which additional factors are involved in this process, or which sequences determine that a promoter will ensure productive transcription. In addition, it cannot be ruled out that tssRNAs have a role on their own.

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