Differential remodeling of the HIV-1 nucleosome upon transcription activators and SWI/SNF complex binding

Here we have examined HIV-1 nucleosome remodeling upon the binding of trans cription factors and the SWI/SNF complex using a novel approach. The approa ch combines UV laser protein-DNA crosslinking, electrophoretic mobility-shi ft analysis and DNase I protection analysis with immunochemical techniques. It was found that single activator-bound HIV-1 nucleosomes exhibit very we ak perturbation in histone NH2 tail-DNA interactions. However, the simultan eous binding of the transcription activators Sp1, NF-kB1, LEF-1 and USF syn ergistically increased the release of histone NH, tails from nucleosomal DN A. In contrast, the binding of SWI/SNF complex to HIV-1 nucleosome disrupte d structured histone domain-DNA contacts, but not histone NH2 tail-DNA inte ractions. Stable remodeled nucleosomes, (obtained after detachment of SWI/S NF), displayed identical structural alterations with those bound to SWI/SNF . These results demonstrate a different in vitro remodeling of the HIV-1 nu cleosome upon the binding of multiple transcription activators and of SWI/S NF complex. (C) 2000 Academic Press.