Molecular Basis of Transcription-Coupled Pre-mRNA Capping

Fuensanta W. Martinez-Rucobo, Rebecca Kohler, Michiel van de Waterbeemd, Albert J.R. Heck, Matthias Hemann, Franz Herzog, Holger Stark, Patrick Cramer

Publikation: Beitrag in FachzeitschriftArtikelBegutachtung


Capping is the first step in pre-mRNA processing, and the resulting 5'-RNA cap is required for mRNA splicing, export, translation, and stability. Capping is functionally coupled to transcription by RNA polymerase (Pol) II, but the coupling mechanism remains unclear. We show that efficient binding of the capping enzyme (CE) to transcribing, phosphorylated yeast Pol II (Pol IIp) requires nascent RNA with an unprocessed 5'-triphosphate end. The transcribing Pol IIp-CE complex catalyzes the first two steps of capping, and its analysis by mass spectrometry, cryo-electron microscopy, and protein crosslinking revealed the molecular basis for transcription-coupled pre-mRNA capping. CE docks to the Pol II wall and spans the end of the RNA exit tunnel to position the CE active sites for sequential binding of the exiting RNA 5' end. Thus, the RNA 5' end triggers its own capping when it emerges from Pol II, to ensure seamless RNA protection from 5'-exonucleases during early transcription.

Seiten (von - bis)1079-1089
FachzeitschriftMolecular Cell
PublikationsstatusVeröffentlicht - 18 Juni 2015
Extern publiziertJa


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