Abstract
BackgroundDynamic changes to the chromatin structure play a critical role in transcriptional regulation. This is exemplified by the Spt6-mediated histone deposition on to histone-depleted promoters that results in displacement of the general transcriptional machinery during transcriptional repression.ResultsUsing the yeast PHO5 promoter as a model, we have previously shown that blocking Spt6-mediated histone deposition on to the promoter leads to persistent transcription in the apparent absence of transcriptional activators in vivo. We now show that the nucleosome-depleted PHO5 promoter and its associated transcriptionally active state can be inherited through DNA replication even in the absence of transcriptional activators. Transcriptional reinitiation from the nucleosome-depleted PHO5 promoter in the apparent absence of activators in vivo does not require Mediator. Notably, the epigenetic inheritance of the nucleosome-depleted PHO5 promoter through DNA replication does not require ongoing transcription.ConclusionOur results suggest that there may be a memory or an epigenetic mark on the nucleosome-depleted PHO5 promoter that is independent of the transcription apparatus and maintains the promoter in a nucleosome-depleted state through DNA replication.
Highlights
Dynamic changes to the chromatin structure play a critical role in transcriptional regulation
As Spt6-mediated chromatin reassembly is absolutely required for PHO5 repression [13], the failure to repress PHO5 following DNA replication in the absence of functional Spt6 (Figure 2(b)) indicated that the chromatin may not be reassembled over the PHO5 promoter following DNA replication in spt6 mutants
We confirmed this prediction by chromatin immunoprecipitation (ChIP) analysis against the Cterminus of histone H3 using primer pairs spanning the TATA box, the UASp2 Pho4 binding site and the region adjacent to the PHO5 promoter (Figure 2(c))
Summary
Dynamic changes to the chromatin structure play a critical role in transcriptional regulation. This is exemplified by the Spt6-mediated histone deposition on to histone-depleted promoters that results in displacement of the general transcriptional machinery during transcriptional repression. Histone removal is required to allow access of the general transcription machinery to the promoter in order to initiate transcription [1,12]. Chromatin reassembly at the promoter is mediated by the histone chaperone Spt and is essential for transcriptional repression because the histones effectively compete with the general transcription machinery for occupancy at the PHO5 promoter [13]. Pho binding to the DNA initiates depletion of the four positioned nucleosomes that normally reside (page number not for citation purposes)
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