FIG. 10.

Model of a switch of the HPV E6 promoter between repression by CDP/Cut, HDAC1, and two specifically positioned nucleosomes (top) and activation by interaction between unknown components of the nuclear matrix and cellular transcription factors (bottom). The figure shows 12 CDP/Cut binding sites in two MARs flanking the EP segment of HPV-16 and in a silencer motif that overlaps with the binding site of the viral replication origin, as well as the binding site of the replication protein E1 and of the most extensively researched transcriptional regulators. Elements identified previously are the MAR (62), the enhancer and its elements (46), the silencer elements (47 and 48), the replication origin (46), and the promoter elements (17 and 63). Abbreviations for genes: L1, L1 gene; E6, E6 gene; E7, E7 gene. Abbreviations for transcription factor binding sites: AP1, activator protein 1; CDP, CCAAT displacement factor/Cut; GR, glucocorticoid receptor; NFI, nuclear factor 1; TF1, transcription enhancer factor 1; oct, octamer binding factor 1.