5′-Capping enzymes are targeted to pre-mRNA by binding to the phosphorylated carboxy-terminal domain of RNA polymerase II

doi:10.1101/gad.11.24.3306

5′-Capping enzymes are targeted to pre-mRNA by binding to the phosphorylated carboxy-terminal domain of RNA polymerase II

Amgen Institute and Ontario Cancer Institute, Toronto, Ontario M5G 2C1, Canada; ¹Department of Medical Biophysics, University of Toronto, Toronto, Canada; ² Amgen, Inc., Thousand Oaks, California 91320 USA; ³Memorial Sloan-Kettering Cancer Center, New York, New York 10021 USA

Abstract

We have investigated the role of the RNA Polymerase II (Pol II) carboxy-terminal domain (CTD) in mRNA 5′ capping. Transcripts made in vivo by Pol II with a truncated CTD had a lower proportion of capped 5′ ends than those made by Pol II with a full-length CTD. In addition, the enzymes responsible for cap synthesis, RNA guanylyltransferase, and RNA (guanine-7)-methyltransferase bound directly to the phosphorylated, but not to the nonphosphorylated, form of the CTD in vitro. These results suggest that: (1) Pol II-specific capping of nascent transcripts in vivo is enhanced by recruitment of the capping enzymes to the CTD and (2) capping is co-ordinated with CTD phosphorylation.