Much attention has focused on the series of sequence elements upstream of the transcriptional initiation site in the U3 region of the LTR including the Sp1 and NF-kappaB binding sites .
much attention has focused on the series of sequence elements upstream of the transcriptional initiation site in the u3 region of the ltr including the sp1 and nf-kappab binding sites .
O O O O O O O O O O O O O B-DNA_domain_or_region I-DNA_domain_or_region I-DNA_domain_or_region O O B-DNA_domain_or_region I-DNA_domain_or_region O O B-DNA_domain_or_region O O B-protein_molecule O B-protein_complex B-DNA_domain_or_region I-DNA_domain_or_region O