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Updated: Jun 13, 2026

Artificial RNA Polymerase II Elongation Complexes for Dissecting Co-transcriptional RNA Processing Events
Published on: May 13, 2019
The integrator complex recognizes a new double mark on the RNA polymerase II carboxyl-terminal domain
Sylvain Egloff1, Sylwia Anna Szczepaniak, Martin Dienstbier
1Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, United Kingdom.
Abstract:
The carboxyl-terminal domain (CTD) of the largest subunit of RNA polymerase II (pol II) comprises multiple tandem repeats of the heptapeptide Tyr(1)-Ser(2)-Pro(3)-Thr(4)-Ser(5)-Pro(6)-Ser(7). This unusual structure serves as a platform for the binding of factors required for expression of pol II-transcribed genes, including the small nuclear RNA (snRNA) gene-specific Integrator complex. The pol II CTD specifically mediates recruitment of Integrator to the promoter of snRNA genes to activate transcription and direct 3' end processing of the transcripts. Phosphorylation of the CTD and a serine in position 7 are necessary for Integrator recruitment. Here, we have further investigated the requirement of the serines in the CTD heptapeptide and their phosphorylation for Integrator binding. We show that both Ser(2) and Ser(7) of the CTD are required and that phosphorylation of these residues is necessary and sufficient for efficient binding. Using synthetic phosphopeptides, we have determined the pattern of the minimal Ser(2)/Ser(7) double phosphorylation mark required for Integrator to interact with the CTD. This novel double phosphorylation mark is a new addition to the functional repertoire of the CTD code and may be a specific signal for snRNA gene expression.
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