Adeno-associated virus major Rep78 protein disrupts binding of TATA-binding protein to the P97 promoter of human papillomavirus type 16

Adeno-associated virus type 2 (AAV) is known to inhibit the: promoter activ ities of several oncogenes and viral genes, including the human papillomavi rus type 16 (HPV-16) E6 and E7 transforming genes. However, the target elem ents of AAV on the long control region (LCR) upstream of E6 and E7 oncogene s are elusive. A chloramphenicol acetyltransferase assay was performed to s tudy the effect of AAV on the transcription activity of the HPV-16 LCR in S iHa (HPV-positive) and C-33A (HPV-negative) cells. The results reveal that (i) AAV inhibited HPV-16 LCR activity in a dose-dependent manner, (ii) AAV- mediated inhibition did not require the BPV gene products, and (iii) the AA V replication gene product Rep78 was involved in the inhibition. Deletion m utation analyses of the HPV-16 LCR showed that regulatory elements outside the core promoter region of the LCR may not be direct targets of AAV-mediat ed inhibition. Further study with the electrophoretic mobility shift assay demonstrated that Rep78 interfered with the binding of TATA-binding protein (TBP) to the TATA bog of the p97 core promoter more significantly than it disrupted the preformed TBP-TATA complex. These data thus suggest that Rep7 8 may inhibit transcription initiation of the HPV-16 LCR by disrupting the interaction between TBP and the TATA box of the p97 core promoter.