Format

Send to

Choose Destination
Nat Chem Biol. 2018 Dec 17. doi: 10.1038/s41589-018-0188-z. [Epub ahead of print]

Structural basis of 7SK RNA 5'-γ-phosphate methylation and retention by MePCE.

Author information

1
Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, USA.
2
UCLA-U.S. Department of Energy (DOE) Institute of Genomics and Proteomics, University of California, Los Angeles, Los Angeles, CA, USA.
3
Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA, USA. feigon@mbi.ucla.edu.

Abstract

Among RNA 5'-cap structures, γ-phosphate monomethylation is unique to a small subset of noncoding RNAs, 7SK and U6 in humans. 7SK is capped by methylphosphate capping enzyme (MePCE), which has a second nonenzymatic role as a core component of the 7SK ribonuclear protein (RNP), an essential regulator of RNA transcription. We report 2.0- and 2.1-Å X-ray crystal structures of the human MePCE methyltransferase domain bound to S-adenosylhomocysteine (SAH) and uncapped or capped 7SK substrates, respectively. 7SK recognition is achieved by protein contacts to a 5'-hairpin-single-stranded RNA region, thus explaining MePCE's specificity for 7SK and U6. The structures reveal SAH and product RNA in a near-transition-state geometry. Unexpectedly, binding experiments showed that MePCE has higher affinity for capped versus uncapped 7SK, and kinetic data support a model of slow product release. This work reveals the molecular mechanism of methyl transfer and 7SK retention by MePCE for subsequent assembly of 7SK RNP.

PMID:
30559425
DOI:
10.1038/s41589-018-0188-z

Supplemental Content

Full text links

Icon for Nature Publishing Group
Loading ...
Support Center