Iswi subfamily

The archetype of the Iswi subfamily is the Iswi (Imitation SWI2) protein, identified in D melanogaster by homology to Snf2p 1. This protein is at the catalytic core both of the NURF and the ACF/CHRAC chromatin remodelling complexes complexes 2, 3, 4. Biochemical studies favour the ability of Iswi proteins to reposition rather than disrupt nucleosomes. Significantly, all Iswi subfamily proteins require a particular region of the histone H4 tail near the DNA surface as an allosteric effector 5, 6, 7.

Iswi subfamily members participate in a variety of complexes and functional interactions. For example, human SNF2H has been found as part of RSF, hACF/WCRF, hWICH, hCHRAC, NoRC and also associated with cohesin, whilst SNF2L is the catalytic subunit of human NURF (summarised in 8). These are also involved in a variety of functions including activation/repression of initiation and elongation of transcription, replication and chromatin assembly (reviewed in 9, 8, 10, 11. Like the Snf2 subfamily, Iswi subfamily members appear to be adapTable components of many related to the alteration of nucleosome positioning 8.

names associated with subfamily
Isw1p, Isw2p, SMARCA1, SNF2L, SNF2L1, SNF2LB, SMARCA5, hSNF2H
references
1: Elfring, L. K., R. Deuring, et al. (1994). Identification and characterization of Drosophila relatives of the yeast transcriptional activator SNF2/SWI2. Mol Cell Biol 14(4): 2225-34. PubMed
2: Tsukiyama, T., C. Daniel, et al. (1995). ISWI, a member of the SWI2/SNF2 ATPase family, encodes the 140 kDa subunit of the nucleosome remodeling factor. Cell 83(6): 1021-6. PubMed
3: Ito, T., M. Bulger, et al. (1997). ACF, an ISWI-containing and ATP-utilizing chromatin assembly and remodeling factor. Cell 90(1): 145-55. PubMed
4: Varga-Weisz, P. D., M. Wilm, et al. (1997). Chromatin-remodelling factor CHRAC contains the ATPases ISWI and topoisomerase II. Nature 388(6642): 598-602. PubMed
5: Hamiche, A., J. G. Kang, et al. (2001). Histone tails modulate nucleosome mobility and regulate ATP-dependent nucleosome sliding by NURF. Proc Natl Acad Sci U S A 98(25): 14316-21. PubMed
6: Clapier, C. R., K. P. Nightingale, et al. (2002). A critical epitope for substrate recognition by the nucleosome remodeling ATPase ISWI. Nucleic Acids Res 30(3): 649-55. PubMed
7: Fazzio, T. G., M. E. Gelbart, et al. (2005). Two distinct mechanisms of chromatin interaction by the Isw2 chromatin remodeling complex in vivo. Mol Cell Biol 25(21): 9165-74. PubMed
8: Dirscherl, S. S. and J. E. Krebs (2004). Functional diversity of ISWI complexes. Biochem Cell Biol 82(4): 482-9. PubMed
9: Tsukiyama, T. (2002). The in vivo functions of ATP-dependent chromatin-remodelling factors. Nat Rev Mol Cell Biol 3(6): 422-9. PubMed
10: Eberharter, A. and P. B. Becker (2004). ATP-dependent nucleosome remodelling: factors and functions. J Cell Sci 117(Pt 17): 3707-11. PubMed
11: Poot, R. A., L. Bozhenok, et al. (2005). Chromatin remodeling by WSTF-ISWI at the replication site: opening a window of opportunity for epigenetic inheritance? Cell Cycle 4(4): 543-6. PubMed