RT Journal Article SR Electronic(1) A1 Naghavi, Mojgan H. A1 Estable, Mario C. A1 Schwartz, Stefan A1 Roeder, Robert G. A1 Vahlne, AndersYR 2001 T1 Upstream stimulating factor affects human immunodeficiency virus type 1 (HIV-1) long terminal repeat-directed transcription in a cell-specific manner, independently of the HIV-1 subtype and the core-negative regulatory element JF Journal of General Virology, VO 82 IS 3 SP 547 OP 559 DO https://doi.org/10.1099/0022-1317-82-3-547 PB Microbiology Society, SN 1465-2099, AB Human immunodeficiency virus type 1 (HIV-1) is classified into subtypes on the basis of phylogenetic analysis of sequence differences. Inter- and intra-subtype polymorphism extends throughout the genome, including the long terminal repeat (LTR). In this study, the importance of the upstream stimulating factor (USF)-binding site (E-box) in the core-negative regulatory element (NRE) of the LTR of HIV-1 subtypes A, B, C, D, E and G was investigated. In vivo, USF was found to repress transcription directed from representative HIV-1 LTR sequences of all the subtypes tested in an epithelial cell line, yet activate the same transcription in a T-cell line. Mutation of the core-NRE USF site of the representative subtype B LTR did not affect the cell-specific, subtype-independent, dual role of USF. In vitro binding assays showed that recombinant USF43 interacts with the core-NRE from subtypes B and C, but not A, D, E or G. Thus, USF affects LTR-directed transcription in a cell-specific manner, independently of both the HIV-1 subtype from which the LTR was derived and the core-NRE USF site sequences., UL https://www.microbiologyresearch.org/content/journal/jgv/10.1099/0022-1317-82-3-547