Cyclin-Dependent Kinase 12 Increases 3′ End Processing of Growth Factor-Induced c-FOS Transcripts

Abstract

Transcriptional cyclin-dependent kinases (CDKs) regulate RNA polymerase II initiation and elongation as well as cotranscriptional mRNA processing. In this report, we describe an important role for CDK12 in the epidermal growth factor (EGF)-induced c-FOS proto-oncogene expression in mammalian cells. This kinase was found in the exon junction complexes (EJC) together with SR proteins and was thus recruited to RNA polymerase II. In cells depleted of CDK12 or eukaryotic translation initiation factor 4A3 (eIF4A3) from the EJC, EGF induced fewer c-FOS transcripts. In these cells, phosphorylation of serines at position 2 in the C-terminal domain (CTD) of RNA polymerase II, as well as levels of cleavage-stimulating factor 64 (Cstf64) and 73-kDa subunit of cleavage and polyadenylation specificity factor (CPSF73), was reduced at the c-FOS gene. These effects impaired 3′ end processing of c-FOS transcripts. Mutant CDK12 proteins lacking their Arg-Ser-rich (RS) domain or just the RS domain alone acted as dominant negative proteins. Thus, CDK12 plays an important role in cotranscriptional processing of c-FOS transcripts.

Supplemental material for this article may be found at http://dx.doi.org/10.1128/MCB.01157-14.

ACKNOWLEDGMENTS

We thank members of both laboratories for help with experiments and useful comments on the manuscript. We also thank Julie Horner at Thermo Scientific for providing ion trap instrumentation for this project.

This work was supported by National Institutes of Health CARE Center Grant U19 AI076113 (David Margolis, principal investigator [PI]), HARC Center Grant P50 GM082250 (Alan Frankel and Nevan Krogan, co-PIs), P01 AI090935 (Sumit Chandra, PI), P50 GM081879 (Wendell Lim, PI), and RO1 AI049104 (B.M.P., PI). S.J. and K.F. were supported by the California HIV/AIDS Research Program.