UV-vulnerability of human papilloma virus type-16 E7-expressing astrocytes is associated with mitochondrial membrane depolarization and caspase-3 activation.
The human papilloma virus-type 16 (HPV-16) E6 and E7 proteins interact with the p53 and pRb tumor suppressor proteins, respectively. The effect of E6 or E7 expression on UV irradiation (5 and 20 J/m2)-induced genotoxic injury of confluent primary murine astrocytes was determined. Retroviral vectors were used to overexpress E6 and E7. Astrocytes expressing E7 showed increased vulnerability to UV-induced apoptosis while E6 over expressing astrocytes were protected 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 activated 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% after UV-irradiation while the depolarization in control cells was about 50%. E6 overexpression decreased while E7 overexpression increased UV-induced astrocyte apoptosis.
Lee
Won Taek
WT
Department of Anatomy, Yonsei University College of Medicine, Seoul, Korea;
Lee
Sung Ho
SH
Carriedo
Sean G
SG
Giffard
Rona G
RG
Yoon
Yeon Jung
YJ
Kim
Ji Hyung
JH
Park
Kyung Ah
KA
Lee
Jong Eun
JE
D001253:Astrocytes / Q000528:radiation effects*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D005434:Flow Cytometry; D006801:Humans; D008564:Membrane Potentials / Q000502:physiology; D008928:Mitochondria / Q000378:metabolism; D009856:Oncogene Proteins, Viral / Q000528:radiation effects*; D027383:Papillomaviridae / Q000528:radiation effects*; D050725:Papillomavirus E7 Proteins; D012097:Repressor Proteins; D014466:Ultraviolet Rays
C068651:E6 protein, Human papillomavirus type 16; D009856:Oncogene Proteins, Viral; D050725:Papillomavirus E7 Proteins; D012097:Repressor Proteins; C059731:oncogene protein E7, Human papillomavirus type 16; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases