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.
Conference Article| July 22 2008
Expression of human snRNA genes from beginning to end
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Sylvain Egloff, Dawn O'Reilly, Shona Murphy; Expression of human snRNA genes from beginning to end. Biochem Soc Trans 1 August 2008; 36 (4): 590–594. doi: https://doi.org/10.1042/BST0360590
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