Immunodepletion studies show that PTF beta is required for transcription of both classes of snRNA genes in vitro .
immunodepletion studies show that ptf beta is required for transcription of both classes of snrna genes in vitro .
O O O O B-protein_subunit I-protein_subunit O O O O O O O O B-DNA_family_or_group I-DNA_family_or_group O O O