Final answer:
Replication-independent nucleosome assembly is influenced by histone and DNA modifications, the FACT protein complex's role in transcription, and the accessibility of DNA for transcription factors to bind and regulate gene expression.
Step-by-step explanation:
The factors involved in replication-independent nucleosome assembly include various modifications to histones and DNA that influence the spacing and interaction of nucleosomes. One key protein complex essential to this process is FACT (facilitates chromatin transcription), which helps in repositioning nucleosomes during transcription by temporarily removing histones from DNA, allowing polymerase to transcribe DNA into pre-mRNA.
After transcription, FACT assists in replacing the histones to restore the nucleosomes. Another important factor is the methylation of DNA and histones, which leads to tighter packing of nucleosomes and consequently inhibits the binding of transcription factors, turning off gene expression.
DNA accessibility is also essential for active gene expression. When nucleosomes are spaced far apart, DNA becomes exposed, allowing transcription factors to bind and activate gene expression. Conversely, when nucleosomes are closely spaced due to modifications like methylation, gene expression is repressed because transcription factors cannot access the DNA.