Regulation of apoptosis by the papillomavirus E6 oncogene

Abstract

Infection with human papillomaviruses is strongly associated with the development of multiple cancers including esophageal squamous cell carcinoma. The HPV E6 gene is essential for the oncogenic potential of HPV. The regulation of apoptosis by oncogene has been related to carcinogenesis closely; therefore, the modulation of E6 on cellular apoptosis has become a hot research topic recently. Inactivation of the pro-apoptotic tumor suppressor p53 by E6 is an important mechanism by which E6 promotes cell growth; it is expected that inactivation of p53 by E6 should lead to a reduction in cellular apoptosis, numerous studies showed that E6 could in fact sensitize cells to apoptosis. The molecular basis for apoptosis modulation by E6 is poorly understood. In this article, we will present an overview of observations and current understanding of molecular basis for E6-induced apoptosis.

Figure 1

Sequence of HPV-16 E6 protein. Single-letter designations are used to represent the amino acids. The sequence is arranged into a zinc finger configuration. The amino acid residues (₁₂₁KKQR₁₂₄) essential for nuclear import and the PDZ domain-binding motif (₁₄₈ETQL₁₅₁) are marked. T₁₄₉ is a putative phosphorylation site for protein kinase A.

Figure 2

Modulation of apoptosis by E6.