The human papilloma virus-type 16 (HPV-16) E6 and E7 proteins interact with the p53 and pRb tumor sup-pressor proteins, respectively. The effect of E6 or E7 expression on UV irradiation (5 and 20 J/m2)-induced genotoxic injury of confluent primary murine astro-cytes was determined. Retroviral vectors were used to overexpress E6 and E7. Astrocytes expressing E7 showed increased vulnerability to UV-induced apop-tosis while E6 over expressing astrocytes were pro-tected from the same insults. Cell death in the E7 overexpressing cells was apoptotic because it showed DNA ladders, activation of caspase-3, formation of apoptotic bodies and decreased DNA content to less than the G0 level. After UV-irradiation the level of E2F1 in E7-expressing astrocytes was higher than E6-, LXSN- or mock-infected cells, and caspase-3 was acti-vated to a greater extent. E7-expressing astrocytes showed the highest levels of Bax under normal growth conditions. The mitochondrial membrane potential of E7-expressing astrocytes was depolarized by 90% af-ter UV-irradiation while the depolarization in control cells was about 50%. E6 overexpression decreased while E7 overexpression increased UV-induced astro-cyte apoptosis.

Keywords: Human Papill, Astrocyte, Bax, Caspase-3, Apoptosis