The 5'-positive regulatory unit , consisting of the promoter and the 5' enhancer , is already active at the CD4 - CD8 -double-negative ( DN ) stage of development .
the 5'-positive regulatory unit , consisting of the promoter and the 5' enhancer , is already active at the cd4 - cd8 -double-negative ( dn ) stage of development .
O B-DNA_domain_or_region I-DNA_domain_or_region I-DNA_domain_or_region O O O O B-DNA_domain_or_region O O B-DNA_domain_or_region I-DNA_domain_or_region O O O O O O B-protein_molecule O B-protein_molecule O O O O O O O O