How does chromatin remodeling influence gene expression?

• A. Adding acetyl groups to histones to silence genes.
• B. Repositioning or removal of nucleosomes to expose DNA, enabling transcription factor access and activation.
• C. Degrading RNA transcripts to regulate expression.
• D. Splicing of introns from pre-mRNA.

Answer: (B)

Chromatin remodeling controls whether the DNA is accessible to the transcription machinery. By repositioning or removing nucleosomes, the tightly wrapped DNA is exposed, especially at promoters and enhancers, so transcription factors can bind and recruit RNA polymerase to activate transcription. This open chromatin state, often called euchromatin, makes genes more likely to be expressed. Remodeling complexes literally change the packaging to switch genes on or off, and histone modifications often accompany this process to reinforce accessibility.

Adding acetyl groups to histones typically loosens DNA-histone interactions and promotes gene activation, so saying it silences genes isn’t accurate. Degrading RNA transcripts or splicing pre-mRNA occur after transcription or on the RNA itself, not through changes in chromatin structure, so they don’t explain how chromatin remodeling influences expression.