Epigenetic inheritance of an inducibly nucleosome-depleted promoter and its associated transcriptional state in the apparent absence of transcriptional activators

Background: 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. Results: Using 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 nucleosomedepleted 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. Conclusion: Our 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.