Which chromatin remodeling complex reposition or evict nucleosomes to alter DNA accessibility and regulate transcription?

• A. SWI/SNF remodelers reposition or evict nucleosomes to alter DNA accessibility and regulate transcription
• B. DNA methyltransferases modify DNA methylation
• C. ISWI remodelers reposition or evict nucleosomes
• D. Topoisomerases relieve DNA supercoiling

Answer: (A)

Chromatin remodeling complexes use energy from ATP to move or remove histone octamers, changing how accessible DNA is to transcription factors and RNA polymerase. The SWI/SNF remodelers are especially known for actively sliding nucleosomes along DNA or evicting them, which exposes promoter and enhancer DNA and helps initiate or regulate transcription. This ability to open up chromatin by repositioning or removing nucleosomes directly links chromatin structure to transcriptional control, making SWI/SNF remodelers the right example for how chromatin remodeling alters DNA accessibility to regulate gene expression. In contrast, DNA methyltransferases modify DNA methylation without changing nucleosome positions, ISWI remodelers primarily affect nucleosome spacing and higher-order compaction rather than eviction to open chromatin, and topoisomerases adjust DNA supercoiling rather than nucleosome positioning.