RAPID AND PHOSPHOINOSITOL-DEPENDENT BINDING OF THE SWI SNF-LIKE BAF COMPLEX TO CHROMATIN AFTER T-LYMPHOCYTE RECEPTOR SIGNALING/

Lymphocyte activation is accompanied by visible changes in chromatin s tructure. We find that antigen receptor signaling induces the rapid as sociation of the BAF complex with chromatin. PIP2, which is regulated by activation stimuli, is sufficient in vitro to target the BAF comple x to chromatin, but it has no effect on related chromatin remodeling c omplexes containing SNF2L or hISWI. Purification and peptide sequencin g of the subunits of the complex revealed beta-actin as well as a nove l actin-related protein, BAF53. beta-actin and BAF53 are required for maximal ATPase activity of BRG1 and are also required with BRG1 fair a ssociation of the complex with chromatin/matrix. This work indicates t hat membrane signals control the activity of the mammalian SWI/SNF or BAF complex and demonstrates a direct interface between signaling and chromatin regulation.