COMPONENTS OF THE HUMAN SWI SNF COMPLEX ARE ENRICHED IN ACTIVE CHROMATIN AND ARE ASSOCIATED WITH THE NUCLEAR MATRIX/

Biochemical and genetic evidence suggest that the SWI/SNF complex is i nvolved in the remodeling of chromatin during gene activation. We have used antibodies specific against three human subunits of this complex to study its subnuclear localization, as well as its potential associ ation with active chromatin and the nuclear skeleton. Immunofluorescen ce studies revealed a punctate nuclear labeling pattern that was exclu ded from the nucleoli and from regions of condensed chromatin. Dual la beling failed to reveal significant colocalization of BRG1 or hBRM pro teins with RNA polymerase II or with nuclear speckles involved in spli cing. Chromatin fractionation experiments showed that both soluble and insoluble active chromatin are enriched in the hSWI/SNF proteins as c ompared with bulk chromatin, hSWI/SNF proteins were also found to be a ssociated with the nuclear matrix or nuclear scaffold, suggesting that a fraction of the hSWI/SNF complex could be involved in the chromatin organization properties associated with matrix attachment regions.