The transcription factor Spi-1/PU . 1 as well as the closely related factor Spi-B bound to the PU-box in B-cells .
the transcription factor spi-1/pu . 1 as well as the closely related factor spi-b bound to the pu-box in b-cells .
O B-protein_family_or_group I-protein_family_or_group B-protein_molecule I-protein_molecule I-protein_molecule O O O O O O O B-protein_molecule O O O B-DNA_domain_or_region O O O