CCAAT DISPLACEMENT PROTEIN, A REGULATOR OF DIFFERENTIATION-SPECIFIC GENE-EXPRESSION, BINDS A NEGATIVE REGULATORY ELEMENT WITHIN THE 5'-END OF THE HUMAN PAPILLOMAVIRUS TYPE-6 LONG CONTROL REGION

We have reported previously that a 636-bp fragment spanning the 5' two -thirds of the human papillomavirus type 6 (HPV6)-W50 long control reg ion (LCR) functions as a transcriptional silencer (A. Farr, S. Pattiso n, B.-S. Youn, and A. Roman, J. Gen. Virol. 76:827-835, 1995). We have utilized nested deletion analyses to implicate a 66-bp sequence which appears to be critical for this activity. A comparison of the transcr iptional regulatory activities of the LCRs of HPV6-W50 and HPV6b (whic h has a 94-bp deletion, resulting in the elimination of the 66-bp sequ ence) indicates that sequences within the 94-bp region negatively regu late the activity of the intact HPV6 LCR Two sequence-specific DNA-pro tein interactions were visualized via electrophoretic mobility shift a ssays. One of the binding events is mediated by the transcriptional re pressor CCAAT displacement protein (CDP), a factor which is active in undifferentiated cells but inactive in terminally differentiated cells . This conclusion is based on the following three lines of evidence: ( i) a consensus CDP binding site oligonucleotide serves as a competitor in band shift assays, (ii) the band shift complex is not seen when a CDP-negative nuclear extract is used, and (iii) anti-CDP antiserum spe cifically inhibits the binding. These studies identify a DNA-protein i nteraction occurring within the 5' end of the LCR which may be importa nt in maintaining the tight link between keratinocyte differentiation and HPV gene expression.