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. 2017 Oct 4;9(1):30–40. doi: 10.1080/21541264.2017.1338176

Figure 1.

Figure 1.

Ser7 facilitates mRNA capping in S. pombe and snRNA processing in H. sapiens. (A) In S. pombe, Cdk9 (with cyclin partner Pcm1) binds to CTD Ser7P, and enables the recruitment of 5′ cap methyltransferase Pcm1 to a Ser5P CTD. Ser7 is phosphorylated by TFIIH subunit Cdk7/Mcs6, as well as by Bur1. (B) In H. sapiens, the 12-subunit Integrator complex preferentially recognizes a Ser7P-Ser2P CTD at the 3′ end of snRNA genes. Ser7P recruits RPAP2 to the CTD, which dephosphorylates Ser5P, and Integrator is able to recognize both the Ser7P-Ser2P CTD as well as the 3′ box of the snRNA, enabling cleavage and processing of the snRNA. TFIIH subunit Cdk7 phosphorylates Ser7, while phosphatase Ssu72 has been shown to dephosphorylate Ser7P.