Open AccessRequirement of Nhp6 Proteins for Transcription of a Subset of tRNA Genes and Heterochromatin Barrier Function in Saccharomyces cerevisiae
Author(s) -
Priscilla Braglia,
Sandra L. Dugas,
David Donze,
Giorgio Dieci
Publication year - 2007
Publication title -
molecular and cellular biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.14
H-Index - 327
eISSN - 1067-8824
pISSN - 0270-7306
DOI - 10.1128/mcb.00773-06
Subject(s) - biology , saccharomyces cerevisiae , rna polymerase iii , transcription (linguistics) , transfer rna , transcription factor ii d , chromatin , transcription factor , genetics , general transcription factor , rna polymerase ii , enhancer , gene , gene expression , promoter , rna polymerase , rna , linguistics , philosophy
A key event in tRNA gene (tDNA) transcription by RNA polymerase (Pol) III is the TFIIIC-dependent assembly of TFIIIB upstream of the transcription start site. Different tDNA upstream sequences bind TFIIIB with different affinities, thereby modulating tDNA transcription. We found that in the absence of Nhp6 proteins, the influence of the 5'-flanking region on tRNA gene transcription is dramatically enhanced in Saccharomyces cerevisiae. Expression of a tDNA bearing a suboptimal TFIIIB binding site, but not of a tDNA preceded by a strong TFIIIB binding region, was strongly dependent on Nhp6 in vivo. Upstream sequence-dependent stimulation of tRNA gene transcription by Nhp6 could be reproduced in vitro, and Nhp6 proteins were found associated with tRNA genes in yeast cells. We also show that both transcription and silencing barrier activity of a tDNA(Thr) at the HMR locus are compromised in the absence of Nhp6. Our data suggest that Nhp6 proteins are important components of Pol III chromatin templates that contribute both to the robustness of tRNA gene expression and to positional effects of Pol III transcription complexes.