Nucleosome-remodeling enzymes

The nucleotide excision repair pathway recognizes specific distortions in DNA to find the damage and repair it. It is difficult to see how this is achieved when the damage is imbedded in DNA compacted with chromatin. Studies performed in vitro and in vivo indicate that DNA damage present in chromatin or within the nucleosome is actually shielded from repair enzymes. Models have been proposed that invoke chromatin remodeling enzymes to help the NER proteins gain access to the damage, and there is experimental evidence to support them. Several different... 

The RNA polymerase II acquires several special elongation factors, some of which assist the enzyme in dealing with pause sites in the DNA. The accessory proteins (which include nucleosome remodeling factors and a specific elongation factor called FACT) also help RNA polymerase II to pass through nucleosomal arrays in in vitro studies. 

---