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
subfamily sequence logo
Generated using weblogo from alignment of
identified subfamily members for columns where at
least 90% of sequences have residues. Distances
between features may be truncated.
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
