Yeast HMG proteins NHP6A/B potentiate promoter-specific transcriptional activation in vivo and assembly of preinitiation complexes in vitro.
Nonhistone proteins 6A and 6B (NHP6A/B) are nonsequence-specific DNA-binding proteins from Saccharomyces cerevisiae that are related structurally and functionally to the mammalian high mobility group proteins 1 and 2. These DNA architectural proteins distort DNA structure severely and have been shown to promote assembly of specialized recombination complexes. Here we show that the yeast NHP6A/B proteins are required for the induction of a subset of genes transcribed by RNA polymerase II (pol II). Activation of the CUP1, CYC1, GAL1, and DDR2 genes was decreased or abolished completely in the delta nhp6A/B strain. No significant change in basal expression was observed for any of the 10 genes examined. Analysis of chimeric gene constructs localized the regions dependent on NHP6A/B to be primarily at the core promoters, although the GAL1 UAS also requires NHP6A/B for activity. In vitro, NHP6A stimulated transcription by pol II at the GAL1 promoter three- to fivefold above the level of activation by GAL4-VP16 alone. Gel mobility shift assays showed that NHP6A promotes the formation of a complex with TBP and TFIIA at the TATA box that has enhanced affinity for TFIIB.
Paull
T T
TT
Molecular Biology Institute, School of Medicine, University of California, Los Angeles 90095-1737, USA.
Carey
M
M
Johnson
R C
RC
D005656:Fungal Proteins / Q000378:metabolism; D006609:High Mobility Group Proteins / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D012319:RNA Polymerase II / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D016385:TATA Box; D015534:Trans-Activators / Q000378:metabolism; D015533:Transcriptional Activation
D005656:Fungal Proteins; C070633:Gal-VP16; D006609:High Mobility Group Proteins; D015534:Trans-Activators; D012319:RNA Polymerase II