Question

What role does the nucleosome play in gene expression? Specifically discuss how the composition of, modification to, and positioning of the nucleosome can regulate gene expression?

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Answer 1

Role of the nucleosome play in gene expression:

Nucleosomes affect the accessibility of transcription factors to occupy their binding sites in chromatin of eukaryotic cells. The disruption of nucleosome structure within the enhancer/promoter region of the integrated HIV-1 proviral genome is an instructive example of a chromatin remodeling process during transcriptional activation.

• Nucleosomes form the fundamental repeating units of eukaryotic chromatin, which is used to pack the large eukaryotic genomes into the nucleus while still ensuring appropriate access to it.
• Nucleosome can function as barriers to transcription by blocking activators and transcription factors accessing DNA.
• One way to do this is through the positioning of nucleosomes relative to the Transcription Start Sites (TSS). A shift as little as 30 bp between the nucleosome and the TSS can affect gene expression.