Specific up-regulation of DNA polymerase by human papillomavirus 16.
OBJECTIVE
To analyze how the infection of human papillomavirus 16 (HPV16) affects expression of DNA polymerase beta (DNA polB) with the aim of probing the mechanism of over-expression of DNA polB in human cancers.


METHODS
Four fragments of human DNA polB promoter were amplified and constructed into luciferase reporter vector pGL-Basic, generating pGL-BP, pGL-BMH, pGL-BMS, and pGL-BAT constructs respectively, and co-transfected with HPV16 or HPV6 into Hep2 cells. Luciferase activity was assayed 48 hours after transfection. Semi-quantitative RT-PCR was used to measure mRNA expression of endogenous DNA polB. Immunohistochemistry and in situ hybridization were used to analyze DNA polB expression and HPV16 or HPV6 infection in 38 cases of cervical lesions respectively.


RESULTS
With co-transfection of HPV16 and DNA polB promoter-driving reporters into Hep2 cells, pGL-BP reporter in full-length DNA polB promoter presented markedly elevated luciferase activities (P < 0.05). However, the other three mutant reporters: pGL-BMH, pGL-BMS, and pGL-BAT, generated no reporting activities in the presence of HPV16 (P > 0.05). On the contrary, all of polB promoter reporters were little stimulated in co-transfection of HPV6 (P > 0.05). The transfection of HPV16 could enhance the endogenous polB mRNA expression compared with that of HPV6 (3.42 vs. 0.80, P < 0.05). The DNA polB expression was found in 8 of 10 HPV16-positive cervical intraepithelial neoplasia grade III (CIN III) cases, while was only found in 3 of 11 HPV6-positive condyloma accuminatum cases, but was negative in all chronic cervicitis cases. The correlation of DNA polB expression with HPV16 infection in cervical lesions was significant (P < 0.05).


CONCLUSIONS
HPV16 is able to specifically stimulate the expression of DNA polB in human epithelial cells through interaction with the core upstream regulatory sequences of DNA polB promoter. Over-expression of DNA polB might be an explanation for the molecular mechanism underlying HPV-related human cancers.
Liu
Song-Nian
SN
Department of Pathology, Baotou Medical College, Baotou, Inner Mongolia 014000.
Bai
Wu-Yun
WY
Frye
Russell M
RM
Hou
Lin
L
Zhang
Bo
B
D002460:Cell Line; D019951:DNA Polymerase beta / Q000235:genetics / Q000378:metabolism*; D005260:Female; D015971:Gene Expression Regulation, Enzymologic; D052162:Human papillomavirus 16 / Q000235:genetics / Q000378:metabolism*; D052163:Human papillomavirus 6 / Q000235:genetics / Q000378:metabolism; D006801:Humans; D030361:Papillomavirus Infections; D011401:Promoter Regions, Genetic; D002583:Uterine Cervical Neoplasms / Q000235:genetics / Q000473:pathology / Q000821:virology
D019951:DNA Polymerase beta