In mammals, the core ISWI ATPase is SNF2H or SNF2L. SNF2L and SNF2H have non-overlapping protein expression patterns in mice51. They are functionally distinct and are found in different complexes, as distinguished by their accessory subunits51 (Table 2). SNF2L is present in the NURF and CERF (CECR2-containing remodelling factor) complexes, whereas SNF2H is present in the NoRC (nucleolar remodelling complex), WICH (WSTF ISWI chromatin remodelling), ACF and human CHRAC complexes. NURF complexes and NoRC are involved in transcriptional activation and repression. By contrast, ACF, CHRAC and WICH complexes are required for the regulation of chromatin structure (including nucleosome assembly and spacing), the replication of DNA through heterochromatin and the segregation of chromosomes51.
