Mammalian capping enzyme complements mutant Saccharomyces cerevisiae lacking mRNA guanylyltransferase and selectively binds the elongating form of RNA polymerase II.

ABSTRACT: 5'-Capping is an early mRNA modification that has important consequences for downstream events in gene expression. We have isolated mammalian cDNAs encoding capping enzyme. They contain the sequence motifs characteristic of the nucleotidyl transferase superfamily. The predicted mouse and human enzymes consist of 597 amino acids and are 95% identical. Mouse cDNA directed synthesis of a guanylylated 68-kDa polypeptide that also contained RNA 5'-triphosphatase activity and catalyzed formation of RNA 5'-terminal GpppG. A haploid strain of Saccharomyces cerevisiae lacking mRNA guanylyltransferase was complemented for growth by the mouse cDNA. Conversion of Lys-294 in the KXDG-conserved motif eliminated both guanylylation and complementation, identifying it as the active site. The K294A mutant r

SUBMITTER: Yue Z 

PROVIDER: S-EPMC24235 | biostudies-literature | 1997 Nov

REPOSITORIES: biostudies-literature