AP1-Related Factors Interact with Simian Immunodeficiency Virus Long Terminal Repeats

The SF1 element (nucleotide -135 to -131) in the U3 region of the simian immunodeficiency virus (SIV) 5' to the NF-kappaB binding site plays a role in basal expression of SIV [Winandy et al., J Virol 66:5216-5223, 1992]. Using the electrophoretic mobility shift assay, we have characterized a specific SF1 binding factor (sf1) in the nuclear fractions of transformed T cells as well as monocytic and macrophage leukemic cells. A strong SF1 binding activity was demonstrated in all cell types. The SF1 binding activity was unaffected by treatment with PMA, PHA, or Ca(2+) ionophore. The HIV-1 long terminal repeat (LTR) 5' to the NF-kappaB site contained a homologous element which showed a specific binding complex of different mobility. The sf1 interacting with SIV LTR was composed of multiple proteins judged from UV crosslinking, some of which might be related to Jun/Fos proteins. Copyright 1996 S. Karger AG, Basel