Nucleosomes and the accessibility problem

Xin Wang, Lu Bai, Gene O. Bryant, Mark Ptashne

Research output: Contribution to journalReview article

26 Scopus citations


Eukaryotic DNA is packaged in nucleosomes. How does this sequestration affect the ability of transcription regulators to access their sites? We cite evidence against the idea that nucleosome positioning is determined primarily by the intrinsic propensities of DNA sequences to form nucleosomes - such that, for example, regulatory sites would be 'nucleosome-free'. Instead, studies in yeast show that nucleosome positioning is primarily determined by specific DNA-binding proteins. Where nucleosomes would otherwise compete with regulatory protein binding (a modest but potentially biologically important effect), this obstacle can be relieved by at least two strategies for exposing regulatory sites. In contrast to their lack of effect on nucleosome positioning, DNA sequence differences do directly affect both the efficiencies with which nucleosomes form in regions flanking regulatory sites before induction, and the extent of their removal upon induction. These nucleosomes, evidently, inhibit basal transcription but are poised to be removed quickly upon command.

Original languageEnglish (US)
Pages (from-to)487-492
Number of pages6
JournalTrends in Genetics
Issue number12
Publication statusPublished - Dec 1 2011


All Science Journal Classification (ASJC) codes

  • Genetics

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