TRRAP and GCN5 are used by c-Myc to activate RNA polymerase Ⅲ transcription

摘要

Activation of RNA polymerase (pol) Ⅱ transcription by c-Myc generally involves recruitment of histone acetyltransferases and acet-ylation of histones H3 and H4. Here, we describe the mechanism used by c-Myc to activate pol Ⅲ transcription of tRNA and 5S rRNA genes. Within 2 h of its induction, c-Myc appears at these genes along with the histone acetyltransferase GCN5 and the cofactor TRRAP. At the same time, occupancy of the pol Ⅲ-specific factor TFⅢB increases and histone H3 becomes hyperacetylated, but increased histone H4 acetylation is not detected at these genes. The rapid acetylation of histone H3 and promoter assembly of TFⅢB, c-Myc, GCN5, and TRRAP are followed by recruitment of pol Ⅲ and transcriptional induction. The selective acetylation of histone H3 distinguishes pol Ⅲ activation by c-Myc from mechanisms observed in other systems.