Identification of a negative regulatory domain in the human papillomavirus type 18 promoter: interaction with the transcriptional repressor YY1.

The human papillomavirus type 18 (HPV-18) promoter contains a TPA responsive element (TRE) which confers TPA responsiveness on a heterologous promoter. In the context of the HPV-18 promoter, however, this AP-1 site is inactive. We have identified a negative regulatory domain in the HPV-18 promoter which represses the constitutive and TPA-induced AP-1 activity. This negative regulatory sequence has been mapped to 44 nucleotides (OL13). We identified this element as a transcriptional silencer based on its ability to interfere with transcriptional initiation. This HPV-18 silencer domain was narrowed down further to 23 nucleotides, the OL13B element, which bears similarity to three other silencer sequences, present in the mouse N-ras gene upstream regulatory region, the mouse albumin gene enhancer and the adeno-associated virus P5 promoter. The transcriptional repressor protein YY1, which negatively regulates the P5 promoter, binds to the HPV-18 silencer with high affinity. Mutation of the YY1 binding site leads to an enhanced activity of the HPV-18 promoter, strongly suggesting that YY1 plays an important role in controlling HPV-18 early gene expression.