Revealing highly conserved regions in the E6 protein among distinct human papillomavirus types using comparative analysis of multiple sequence alignments

The HPV genome is approximately 8 kb in length and is divided into three regions, the non-coding long control region, and the protein coding early and late regions. The viral genome encodes six early and two late proteins. HPV E6 and E7 genes encode oncoproteins that cause transformation of the host cell, whose action is involved in maintenance of the HPV genome extrachromosomally. Since HPV immortalisation of keratinocytes in vitro has been identified as an important step in tumor progression in vivo, some studies have provided strong experimental supports for the hypothesis that the maintenance and expression of E6 and E7 proteins observed in human cervical carcinomas has pathologic significance. The E6 protein in high risk HPV genotypes has been reported to prevent apoptosis by a p53-independent mechanism which involves inhibition of bax gene expression and degradation of Bax protein in human keratinocytes, resulting in inhibition of apoptosis and therefore cells accumulate mutations in their DNA.