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Abstract:
In different phases of the transcription cycle, RNA polymerase (Pol) II recruits various factors
via its C-terminal domain (CTD), which consists of conserved heptapeptide repeats with the
sequence Tyr1-Ser2-Pro3-Thr4-Ser5-Pro6-Ser7. We show that the CTD of transcribing yeast Pol II is
phosphorylated at Tyr1, in addition to Ser2, Thr4, Ser5, and Ser7. Tyr1 phosphorylation stimulates
binding of elongation factor Spt6 and impairs recruitment of termination factors Nrd1, Pcf11, and
Rtt103. Tyr1 phosphorylation levels rise downstream of the transcription start site and decrease
before the polyadenylation site, largely excluding termination factors from gene bodies. These results
show that CTD modifications trigger and block factor recruitment and lead to an extended CTD
code that explains transcription cycle coordination on the basis of differential phosphorylation of
Tyr1, Ser2, and Ser5.
