The carboxy-terminal domain (CTD) of the large subunit of RNA polymerase II (Pol II), RBP1, consists of repeats of the sequence YSPTSPS. Post-transcriptional modifications at specific CTD residues are crucial for transcriptional regulation, and two studies now describe a role for RBP1 Tyr1 phosphorylation in mammalian cells. Substitution of Tyr1 residues in CTD repeats led to the partial degradation of RPB1 to a truncated, 'CTD-less' form, which suggests a role of this residue in RBP1 stability. Furthermore, Descostes et al. showed that phosphorylated Tyr1 is associated with the 5′ end of gene promoters and antisense transcription, and Hsin et al. reported that Tyr1 phosphorylation has a role in the expression of upstream antisense transcripts. Thus, Tyr1 phosphorylation of the CTD functions in Pol II stability and may control promoter directionality.
References
Hsin, J.-P. et al. RNAP II CTD tyrosine 1 performs diverse functions in vertebrate cells. eLife http://dx.doi.org/10.7554/eLife.02112 (2014)
Descostes, N. et al. Tyrosine phosphorylation of RNA Polymerase II CTD is associated with antisense promoter transcription and active enhancers in mammalian cells. eLife http://dx.doi.org/10.7554/eLife.02105 (2014)
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Du Toit, A. CTD Tyr1 gives direction. Nat Rev Mol Cell Biol 15, 367 (2014). https://doi.org/10.1038/nrm3814
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DOI: https://doi.org/10.1038/nrm3814
