Chromatin structure remodeling (RSC) complex
RSC (Remodelling the Structure of Chromatin) is a member of the ATP-dependent chromatin remodeller family (other members being the SWI/SNF, INO80, ISW1 and CHD complexes). RSC consists of 17 subunits and exhibits a DNA-dependent ATPase activity stimulated by both free and nucleosomal DNA and a capacity to perturb nucleosome structures. It is at least 10-fold more abundant than the SWI/SNF complex and is essential for mitotic growth.
Generation of loops in dsDNA
A single molecule study using magnetic tweezers has observed that RSC generates DNA loops in vitro while simultaneously generating negative supercoils in the template. The figure above [removed 16 September 2012] shows three AFM images from that study. On the left, a single RSC complex is bound to the end of a dsDNA template. The center image shows a DNA loop generated by RSC. The image on the right shows a loop generated by RSC, which contains supercoils.
The current model of translocation on dsDNA is shown in the figure to the right, whereby RSC binds the DNA at two locations. Hydrolysis of ATP allows the complex to translocate the DNA into a loop. RSC can release the loop either by translocating back to the original state at a comparable velocity, or by losing one of its two contacts.
The following is list of RSC components that have been identified in yeast and the corresponding human orthologs:
|RSC6||SMARCD1, SMARCD2, SMARCD3|
- SWI/SNF (nucleosome remodeling complex)
- Transcription coregulator
- Imitation SWI (nucleosome remodeling complex)
- Cairns BR, Lorch Y, Li Y, Zhang M, Lacomis L, Erdjument-Bromage H, Tempst P, Du J, Laurent B, Kornberg RD (1996). "RSC, an essential, abundant chromatin-remodeling complex". Cell. 87 (7): 1249–60. doi:10.1016/S0092-8674(00)81820-6. PMID 8980231.
- Lia G, Praly E, Ferreira H, Stockdale C, Tse-Dinh YC, Dunlap D, Croquette V, Bensimon D, Owen-Hughes T (2006). "Direct observation of DNA distortion by the RSC complex". Mol. Cell. 21 (3): 417–25. doi:10.1016/j.molcel.2005.12.013. PMC . PMID 16455496.