Native and recombinant capping enzymes block transcription in vitro.
Tempst/Elsevier
The authors have found that the two yeast mRNA capping enzymes, Cet1p and Ceg1p, are potent in vitro inhibitors of transcription. Cet1p, stimulated by its Ceg1p binding partner, stalled transcription by blocking reinitiation at already activated promoters. Conversely, elimination of Cet1p in vivo stimulated transcription. Although Cet1p is the first general repressor found to act at reinitiation, this step is well suited for transcription inhibition. “If 100 transcripts are made from a promoter,” says Myers, “only one is made at initiation—the remaining 99 are made by reinitiation.”
A block by the capping enzyme could ensure that RNA polymerase does not make more transcripts than can...
