NF-dBhomodimerbinding within theHIV-1initiator region and interactions withTFII-I

Weshowthat thebinding ofRelp50andp52 homodimers atsites within thetranscriptional initiation region ofHIV-1provides fortheir ability tointeract withother proteins thatbindtheinitiator. Thebinding ofonesuch protein, theinitiator protein TFII-I, totheinitiation region of HIV-1isaugmented inthepresence ofRelp50andRelp52 homodimers. Consistent withthis, invitro Relhomodimers potentiate HIV-1transcription inamannerdependent upon TFII-I. Thefindings suggest thatReldimers mayregulate HIV-1transcription intwoways. First, through binding atthe icBenhancer sites at(-104to-80), NF-cBp5O:p65 partic- ipates inclassical transcriptional activation. Second, Reldimers suchasp59orp52might bindatinitiator sequences toregulate thedenovobinding ofcomponents ofcertain preinitiation complexes. These findings, andtheexistence ofRelbinding sites attheinitiators ofother genes, suggest roles forRelproteins in early events determining transcriptional control.