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Crystal structure of mammalian capping enzyme (Mce1) and Pol II CTD complexCrystal structure of mammalian capping enzyme (Mce1) and Pol II CTD complex
Structural highlights
FunctionMCE1_MOUSE Bifunctional mRNA-capping enzyme exhibiting RNA 5'-triphosphatase activity in the N-terminal part and mRNA guanylyltransferase activity in the C-terminal part. Catalyzes the first two steps of cap formation: by removing the gamma-phosphate from the 5'-triphosphate end of nascent mRNA to yield a diphosphate end, and by transferring the gmp moiety of GTP to the 5'-diphosphate terminus. Publication Abstract from PubMedPhysical interaction between the phosphorylated RNA polymerase II carboxyl-terminal domain (CTD) and cellular capping enzymes is required for efficient formation of the 5' mRNA cap, the first modification of nascent mRNA. Here, we report the crystal structure of the RNA guanylyltransferase component of mammalian capping enzyme (Mce) bound to a CTD phosphopeptide. The CTD adopts an extended beta-like conformation that docks Tyr1 and Ser5-PO(4) onto the Mce nucleotidyltransferase domain. Structure-guided mutational analysis verified that the Mce-CTD interface is a tunable determinant of CTD binding and stimulation of guanylyltransferase activity, and of Mce function in vivo. The location and composition of the CTD binding site on mammalian capping enzyme is distinct from that of a yeast capping enzyme that recognizes the same CTD primary structure. Thus, capping enzymes from different taxa have evolved different strategies to read the CTD code. Structural insights to how mammalian capping enzyme reads the CTD code.,Ghosh A, Shuman S, Lima CD Mol Cell. 2011 Jul 22;43(2):299-310. Epub 2011 Jun 16. PMID:21683636[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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