Binds to scaffold/matrix attachment region (S/MAR) DNA and forms a molecular assembly point to allow the formation of a 'transcriptosomal' complex (consisting of SR proteins and RNA polymerase II) coupling transcription and RNA processing. Functions as an estrogen receptor corepressor and can also bind to the HSP27 promoter and decrease its transcription. Thereby acts as a negative regulator of cell proliferation. When associated with RBMX, binds to and stimulates transcription from the SREBF1 promoter 