Practice question

Nucleosome core particle contains one hundred forty-seven base pairs of DNA wrapped around octamer of histones with central H3-H4 tetramer and two peripheral H2A-H2B dimers. To transcribe through chromatin, RNA polymerase II needs partial disassembly. FACT binds to nucleosome and destabilizes dimer-tetramer contacts, causing transient eviction of one H2A-H2B dimer converting nucleosome to hexasome, unwrapping approximately thirty base pairs of entry DNA. This reduction lowers mechanical barrier, decreasing polymerase crossing time measured by optical tweezers. FACT then acts as chaperone to redeposit dimer after passage.