Figure 16.

Putative schematic representation of the nuclear factors binding to their respective DNA sites in the intragenic HS7 region of HIV-1. This assignment is based on in vitro binding studies. Moreover, the transcription factors Oct-1, Sp1, Sp3 and PU.1 have also been demonstrated by ChIP assays to be recruited to the HS7 region in vivo in the chromosomal context of integrated proviruses. The DNA-binding sites are represented as closed rectangles. The ubiquitous nuclear factors are represented as gray-shaded ovals, whereas factors specific to a given cell line appear as open circles. Our experiments do not establish whether the nuclear factors indeed bind together, successively or alternatively to their cognate DNA sequences.