Human TFIIIC Relieves Chromatin-Mediated Repression of RNA Polymerase III Transcription and Contains an Intrinsic Histone Acetyltransferase Activity

Abstract

Human TFIIIC is a multisubunit factor that is essential for transcription by RNA polymerase III on tRNA and virus-associated RNA genes and initiates preinitiation complex assembly by direct recognition of promoter elements. We show that highly purified TFIIIC, at concentrations above those sufficient for transcription of naked DNA templates, effectively relieves nucleosome-mediated repression on an in vitro-reconstituted chromatin template. Highly purified TFIIIC alone can bind to the A and B boxes of a tRNA gene within a chromatin template and, further, displays a histone acetyltransferase activity that is intrinsic to at least one (and probably three) of its subunits. The possibility of a direct link between TFIIIC-dependent chromatin transcription and acetyltransferase activities is suggested by the partial loss of these activities, but not DNA transcription activity, following pretreatment of TFIIIC with p-hydroxymercuribenzoic acid.

ACKNOWLEDGMENTS

We thank Y. Nakatani for the p300 HAT domain expression vector and for critical comments on the manuscript, Tsutomu Ohta for providing the NAP1 expression plasmid, S. Malik for help with the HeLa topoisomerase I purification, and V. Palhan for critical reading of the manuscript.

This work was supported by a grant from the NIH to R.G.R.