Definitions

SWI/SNF

SWI/SNF

SWI/SNF (SWItch/Sucrose NonFermentable) is a yeast nucleosome remodeling complex composed of several proteins - products of the SWI and SNF genes (/, , , ) as well as several other polypeptides. 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:
yeast human function
, contains LXXLL nuclear receptor binding motifs
/ ATP dependent chromatin remodeling
, similar sequence, function unknown
, , similar sequence, function unknown
, actin-like protein

Mechanism of Action

Two mechanisms for nucleosome remodeling by SWI/SNF have been proposed. 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. A recent study 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

References

External links

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