Variations in the composition of mammalian SWI/SNF chromatin remodelling complexes.
The ATP-dependent chromatin remodelling complexes SWI/SNF alter the chromatin structure in transcriptional regulation. Several classes of mammalian SWI/SNF complex have been isolated biochemically, distinguished by a few specific subunits, such as the BAF-specific BAF250A, BAF250B and BRM, and the PBAF-specific BAF180. We have determined the complex compositions using low stringency immunoprecipitation (IP) and shown that the pattern of subunit interactions was more diverse than previously defined classes had predicted. The subunit association at five gene promoters that depend on the SWI/SNF activity varied and the sequential chromatin immunoprecipitations revealed that different class-specific subunits occupied the promoters at the same time. The low-stringency IP showed that the BAF-specific BAF250A and BAF250B and the PBAF-specific BAF180 co-exist in a subset of SWI/SNF complexes, and fractionation of nuclear extract on size-exclusion chromatography demonstrated that sub-complexes with unorthodox subunit compositions were present in the cell. We propose a model in which the constellations of SWI/SNF complexes are "tailored" for each specific chromatin target and depend on the local chromatin environment to which complexes and sub-complexes are recruited.
Ryme
Jessica
J
Department of Cell Biology, The Wenner-Gren Institute, Stockholm University, SE-106 91 Stockholm, Sweden.
Asp
Patrik
P
Böhm
Stefanie
S
Cavellán
Erica
E
Farrants
Ann-Kristin Ostlund
AK
D000818:Animals; D002458:Cell Fractionation; D047369:Chromatin Immunoprecipitation; D002850:Chromatography, Gel; D002868:Chromosomal Proteins, Non-Histone / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D004268:DNA-Binding Proteins; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation; D008322:Mammals / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism; D009707:Nucleosomes / Q000378:metabolism; D009928:Organ Specificity / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D021122:Protein Subunits / Q000378:metabolism; D012492:Salts; D014157:Transcription Factors / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*
C112476:ARID1A protein, human; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D009707:Nucleosomes; C102195:PBRM1 protein, human; D021122:Protein Subunits; C445179:SWI-SNF-B chromatin-remodeling complex; D012492:Salts; D014157:Transcription Factors