Octamer transcription factors up-regulate the expression of CCR5, a coreceptor for HIV-1 entry

T cell activation can induce expression of CCR5, a major coreceptor for macrophage-tropic (R5) human immunodeficiency virus type 1 (HIV-1). Here we report that overexpression of the Oct-2 transcription factor and octamer coactivator BOB.1/OBF/OCA-B, both of which are induced in T cells following T cell receptor signaling, synergistically up-regulates CCR5 promoter activity via interaction with an octamer motif on the promoter. We also show that the octamer transcription factors can increase cell surface expression of CCR5 and fusogenicity of the cells with R5 HIV-1 Env. These results suggest that octamer transcription factors may play a critical role in the induction of CCR5 expression on, and thereby susceptibility to, R5 HIV-1 of T cells following antigenic stimulation.