SWI/SNF 4387046 215546295 2008-05-28T18:01:18Z DOI bot 6652755 Citation maintenance. You can [[WP:DOI|use this bot]] yourself! Please [[User:DOI_bot/bugs|report any bugs]]. [[Image: SNF2-Like Family.jpg|right|thumb|400px|Diagram indicating location of the SNF2 Subfamily of proteins and their relative similarity with other proteins organized by their conservation of NTP-binding motifs.]]'''SWI/SNF''' (SWItch/Sucrose NonFermentable)<ref name="pmid6392017">{{cite journal | author = Neigeborn L, Carlson M | title = Genes affecting the regulation of SUC2 gene expression by glucose repression in Saccharomyces cerevisiae | journal = Genetics | volume = 108 | issue = 4 | pages = 845–58 | year = 1984 | pmid = 6392017 | doi = | issn = | url = http://www.genetics.org/cgi/content/abstract/108/4/845}}</ref><ref name="pmid6436497">{{cite journal | author = Stern M, Jensen R, Herskowitz I | title = Five SWI genes are required for expression of the HO gene in yeast | journal = J. Mol. Biol. | volume = 178 | issue = 4 | pages = 853–68 | year = 1984 | pmid = 6436497 | doi = 10.1016/0022-2836(84)90315-2 | issn = }}</ref> is a [[yeast]] [[nucleosome]] remodeling complex composed of several proteins - products of the SWI and SNF genes ({{Yeast Gene|SWI1}}, {{Yeast Gene|SWI2}}/{{Yeast Gene|SNF2}}, {{Yeast Gene|SWI3}}, {{Yeast Gene|SWI5}}, {{Yeast Gene|SWI6}}) as well as several other polypeptides.<ref name="pmid9118215">{{cite journal | author = Pazin MJ, Kadonaga JT | title = SWI2/SNF2 and related proteins: ATP-driven motors that disrupt protein-DNA interactions? | journal = Cell | volume = 88 | issue = 6 | pages = 737–40 | year = 1997 | pmid = 9118215 | doi = 10.1016/S0092-8674(00)81918-2 | issn = }}</ref> It possesses a DNA-stimulated [[ATPase]] activity and can destabilize [[histone]]-DNA interactions in reconstituted nucleosomes in an [[Adenosine triphosphate|ATP]]-dependent manner, though the exact nature of this structural change is unknown. ==Family members== Below is a list of yeast SWI/SNF family members and human [[ortholog]]s:<ref name="pmid10601972">{{cite journal | author = Collingwood TN, Urnov FD, Wolffe AP | title = Nuclear receptors: coactivators, corepressors and chromatin remodeling in the control of transcription | journal = J. Mol. Endocrinol. | volume = 23 | issue = 3 | pages = 255–75 | year = 1999 | pmid = 10601972 | doi = 10.1677/jme.0.0230255 | issn = }}</ref> {| class="wikitable" |- ! yeast ! human ! function |- | {{Yeast Gene|SWI1}} | {{gene|ARID1A}}, {{gene|ARID1B}} | contains LXXLL [[nuclear receptor]] binding motifs |- | {{Yeast Gene|SWI2}}/{{Yeast Gene|SNF2}} | {{gene|SMARCA4}} | [[Adenosine triphosphate|ATP]] dependent chromatin remodeling |- | {{Yeast Gene|SWI3}} | {{gene|SMARCC1}}, {{gene|SMARCC2}} | similar sequence, function unknown |- | {{Yeast Gene|SWP73}} | {{gene|SMARCD1}}, {{gene|SMARCD2}}, {{gene|SMARCD3}} | similar sequence, function unknown |- | {{Yeast Gene|SWP61}} | {{gene|ACTL6A}}, {{gene|ACTL6b}} | [[actin]]-like protein |} ==Mechanism of Action== Two mechanisms for nucleosome remodeling by SWI/SNF have been proposed.<ref name="pmid12897850">{{cite journal | author = van Holde K, Yager T | title = Models for chromatin remodeling: a critical comparison | journal = Biochem. Cell Biol. | volume = 81 | issue = 3 | pages = 169–72 | year = 2003 | pmid = 12897850 | doi = 10.1139/o03-038 | issn = }}</ref> The first model contends that a unidirectional diffusion of a twist defect within the nucleosomal DNA results in a corkscrew-like propagation of DNA over the octamer surface that initiates at the DNA entry site of the nucleosome. The other is known as the "bulge" or "loop-recapture" mechanism and it involves the dissociation of DNA at the edge of the nucleosome with reassociation of DNA inside the nucleosome, forming a DNA bulge on the octamer surface. The DNA loop would then propagate across the surface of the histone octamer in a wave-like manner, resulting in the repositioning of DNA without changes in the total number of histone-DNA contacts.<ref name="pmid12666181">{{cite journal | author = Flaus A, Owen-Hughes T | title = Mechanisms for nucleosome mobilization | journal = Biopolymers | volume = 68 | issue = 4 | pages = 563–78 | year = 2003 | pmid = 12666181 | doi = 10.1002/bip.10323 | issn = }}</ref> A recent study<ref name="pmid16518397">{{cite journal | author = Zofall M, Persinger J, Kassabov SR, Bartholomew B | title = Chromatin remodeling by ISW2 and SWI/SNF requires DNA translocation inside the nucleosome | journal = Nat. Struct. Mol. Biol. | volume = 13 | issue = 4 | pages = 339–46 | year = 2006 | pmid = 16518397 | doi = 10.1038/nsmb1071 | issn = }}</ref> has provided strong evidence against the twist diffusion mechanism and has further strengthened the loop-recapture model, as proposed in the figure below. [[Image:SWI-SNF_Model.jpg|center|thumb|600px|A study conducted by ''Zofall et al.''<ref name="pmid16518397" /> provided more evidence for the "bulge propagation" mechanism of nucleosome remodeling.]] ==See also== *[[Chromatin Structure Remodeling (RSC) Complex]] *[[Transcription coregulator]] ==References== <references/> [[Category:Enzymes]] {{enzyme-stub}} {{Transcription coregulators}} [[Category:Transcription coregulators]]