Expression of human snRNA genes from beginning to end.
In addition to protein-coding genes, mammalian pol II (RNA polymerase II) transcribes independent genes for some non-coding RNAs, including the spliceosomal U1 and U2 snRNAs (small nuclear RNAs). snRNA genes differ from protein-coding genes in several key respects and some of the mechanisms involved in expression are gene-type-specific. For example, snRNA gene promoters contain an essential PSE (proximal sequence element) unique to these genes, the RNA-encoding regions contain no introns, elongation of transcription is P-TEFb (positive transcription elongation factor b)-independent and RNA 3'-end formation is directed by a 3'-box rather than a cleavage and polyadenylation signal. However, the CTD (C-terminal domain) of pol II closely couples transcription with RNA 5' and 3' processing in expression of both gene types. Recently, it was shown that snRNA promoter-specific recognition of the 3'-box RNA processing signal requires a novel phosphorylation mark on the pol II CTD. This new mark plays a critical role in the recruitment of the snRNA gene-specific RNA-processing complex, Integrator. These new findings provide the first example of a phosphorylation mark on the CTD heptapeptide that can be read in a gene-type-specific manner, reinforcing the notion of a CTD code. Here, we review the control of expression of snRNA genes from initiation to termination of transcription.
Egloff
Sylvain
S
Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford, UK.
O'Reilly
Dawn
D
Murphy
Shona
S
D000818:Animals; D005786:Gene Expression Regulation / Q000235:genetics*; D006801:Humans; D011485:Protein Binding; D012319:RNA Polymerase II / Q000378:metabolism; D012342:RNA, Small Nuclear / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic / Q000235:genetics
D012342:RNA, Small Nuclear; D012319:RNA Polymerase II