ABSTRACT
Chromatin remodeling activities increase the accessibility of the genome to DNA-binding proteins by altering the DNA-histone interaction noncovalently. Chromatin remodeling factors are recruited to particular chromatin regions by site-specific DNA-binding proteins. The eukaryotic protein complex SWI/SNF is probably one of the main contributors to chromatin remodeling by ATP hydrolysis, so we will focus on this one in the following description of ATP-dependent chromatin remodeling. The ATPase activity of the Swi2/Snf2 subunit in yeast is stimulated by double-stranded DNA and is critical for the transcriptional activation and chromatin remodeling functions of the SWI/SNF complex. The remodeling process seems to begin with a small movement of the SWI/SNF complex over approximately 20 bp of DNA upstream from its original binding position. Importantly, genome-wide localization studies have shown that for highly transcribed genes, transcription factors localize to DNA elements closely upstream of transcription start sites in regions that are usually relatively depleted of nucleosomes in comparison with genes having lower levels of expression.
