SWI/SNF

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SWI/SNF (SWItch/Sucrose NonFermentable)^[1][1] is a yeast nucleosome remodeling complex composed of several proteins - products of the SWI and SNF genes (SWI1, SWI2/SNF2, SWI3, SWI5, SWI6) as well as several other polypeptides.^[1] It possesses a DNA-stimulated ATPase activity and can destabilize histone-DNA interactions in reconstituted nucleosomes in an 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 orthologs:^[1]

yeast	human	function
SWI1	ARID1A, ARID1B	contains LXXLL nuclear receptor binding motifs
SWI2/SNF2	SMARCA4	ATP dependent chromatin remodeling
SWI3	SMARCC1, SMARCC2	similar sequence, function unknown
SWP73	SMARCD1, SMARCD2, SMARCD3	similar sequence, function unknown
SWP61	ACTL6A, ACTL6b	actin-like protein

Mechanism of Action

Two mechanisms for nucleosome remodeling by SWI/SNF have been proposed.^[1] 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.^[1] A recent study^[1] has provided strong evidence against the twist diffusion mechanism and has further strengthened the loop-recapture model, as proposed in the figure below.

See also

• Chromatin Structure Remodeling (RSC) Complex
• Transcription coregulator

References

Template:Enzyme-stub

v • d • e Transcription coregulators
Coactivators	CARM1 - CRTC1 - CBP - NCOA1 (SRC-1) - NCOA2 (GRIP1/SRC-2/TIF2) - NCOA3 (AIB/SRC-3/TRAM-1) - NCOA4 - NCOA6 - NCOA7 - PPARGC1A - PPARGC1B - TGFB1I1
Corepressors	NCOR1 - NRIP1 - NCOR2 (SMRT) - PELP-1 - RCOR1 - Rb - SIN3A- SIN3B - Tripartite motif-containing (TRIM24, TRIM28)
ATP-dependent remodeling factors	Chromatin Structure Remodeling (RSC) Complex - SWI/SNF

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Acknowledgement and Attribution Regarding Sources of Content

Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .