The RNA Polymerase II CTD Kinase CTDK-I Affects Pre-mRNA 3′ Cleavage/Polyadenylation through the Processing Component Pti1p

There are several kinases in Saccharomyces cerevisiae that phosphorylate the CTD of RNA polymerase II, but specific and distinct functions of the phospho-CTDs generated by the different kinases are not well understood. A genetic screen for suppressors of loss of yeast CTD kinase I (CTDK-I) function (by deletion of the catalytic subunit gene CTK1) identified PTI1, a potential 3′ cleavage/polyadenylation factor. Genetic and physical interactions connect Pti1p to components of CF IA and CF II/CPF, and mutations of PTI1 or CTK1 affect 3′ cleavage site choice and transcript abundance of particular genes. Therefore, one important function of the CTDK-I-generated phospho-CTD appears to be the coupling of transcription to 3′ processing of pre-mRNAs by a Pti1p-containing complex.