Molecular and phylogenetic analysis of the HPV 16 E4 gene in cervical lesions from women in Greece

The HPV16 E1^∧E4 protein is thought to contribute to the release of newly formed viral particles from infected epithelia. In order to investigate amino acid mutations in the HPV16 E1^∧E4 protein, the complete E4 ORF was amplified by PCR in 27 HPV16-positive cervical samples, and the amplicons were cloned. Fifteen nucleic acid variations were identified in the E4 ORF, including seven silent nucleic acid mutations. In addition, nine amino acid mutations (A7V, A7P, L16I, D45E, L59I, L59T, Q66P, S72F, H75Q) were detected in the E1^∧E4 protein, and these were associated with the severity of cervical malignancy. A maximum-likelihood phylogenetic tree was constructed based on the E4 ORF, and nucleotide sequence analysis of the E4, E6 and E7 genes from the same samples was conducted in order to determine the phylogenetic origin of the cloned sequences from the amplified HPV16 E4. Based on the nucleotide sequence and phylogenetic analysis it was revealed that even though E4 ORF constitutes a small polymorphic portion of the viral genome (288 bp), it could provide valuable information about the origins of the HPV16 genome. In addition, molecular evolutionary analysis of the E4 coding region revealed that neutral selection is dominant in the overlapping region of the E4 and E2 ORFs.