Transcribing RNA Polymerase II Is Phosphorylated at CTD Residue Serine-7

Abstract

RNA polymerase II is distinguished by its large carboxyl-terminal repeat domain (CTD), composed of repeats of the consensus heptapeptide Tyr1-Ser2-Pro3-Thr4-Ser5-Pro6-Ser7. Differential phosphorylation of serine-2 and serine-5 at the 5' and 3' regions of genes appears to coordinate the localization of transcription and RNA processing factors to the elongating polymerase complex. Using monoclonal antibodies, we reveal serine-7 phosphorylation on transcribed genes. This position does not appear to be phosphorylated in CTDs of less than 20 consensus repeats. The position of repeats where serine-7 is substituted influenced the appearance of distinct phosphorylated forms, suggesting functional differences between CTD regions. Our results indicate that restriction of serine-7 epitopes to the Linker-proximal region limits CTD phosphorylation patterns and is a requirement for optimal gene expression.

Two Distinct Roles of ARABIDOPSIS HOMOLOG OF TRITHORAX1 (ATX1) at Promoters and within Transcribed Regions of ATX1-Regulated Genes

“…The rapid addition of Ser5P often results in the detection of this modification in promoter regions (Gomes et al, 2006;Chapman et al, 2007;Kim et al, 2009;Qiu et al, 2009), but the detection of Ser2P at the promoter region of the genes was unusual. To examine whether the signals might originate from lack of specificity of the antibodies, we investigated the specificities of both the Ser5P and Ser2P antibodies against synthetic peptides.…”

“…Pol II retains its Ser5P modification predominantly during the transcription of the first several hundred nucleotides. Therefore, Ser5P is found primarily at the promoter regions and 59-ends of genes and is considered a biochemical marker for transcription initiation and early elongation (Gomes et al, 2006;Chapman et al, 2007;Kim et al, 2009).…”

Serine-7 but not serine-5 phosphorylation primes RNA polymerase II CTD for P-TEFb recognition

“…Phosphorylation of Ser5 by Cdk7 and Cdk8 kinases of TFIIH and the mediator complex, respectively, has been described to be concomitant with transcription initiation, whereas Cdk9 of P-TEFb is suggested to phosphorylate Ser2, which marks the elongation phase of transcription [3][4][5][6][7][8] . In addition, Ser7 of the CTD can also be phosphorylated, which has been linked to small nuclear RNAs (snRNA) transcription and recruitment of the integrator complex [9][10][11][12][13] . Whereas some genes, for example, those on CpG islands, can directly proceed to the elongation state by recruiting P-TEFb to RNAPII 14 , genomewide studies suggest that the majority of genes in higher eukaryotes are under the control of promoter-proximal pausing [15][16][17] .…”

Hyperphosphorylation of RNA Polymerase II in Response to Topoisomerase I Cleavage Complexes and Its Association with Transcription- and BRCA1-dependent Degradation of Topoisomerase I

“…1 During the transcription cycle, serine-2, serine-5, and serine-7 are the main residues subjected to regulatory phosphorylation-dephosphorylation. 1,2 Serine-5 phosphorylation (Ser 5 -P) and serine-2 phosphorylation (Ser 2 -P) are thought to be principally mediated by the kinase activities of TFIIH (Cdk7) and P-TEFb (Cdk9), respectively. The kinase(s) involved in serine-7 phosphorylation (Ser 7 -P) remains to be identified.…”