Functional analysis of CDC7 protein which is interacted with HPV E6

Tong, Seo Yun; Kim, Jung Jin; Cho, Yang Sook; Park, Jong Sup

Abstract

OBJECTIVE
Human papillomaviruses are associated with the majority of cervical cancers. There is a wide effort focused on searching for the target of the involvement of p53-independent HPV-16E6 interacting proteins. We identified Cdc7 (cell division cycle 7-related protein kinases) as a binding partner of E6 and investigated its biological function in cervical cancer cells.
METHODS
The baits, E6, fused to the LexA-BD subunit using pBTM116 vector were used to screen an oligoneucleotide primed human HeLa cDNA library cloned in pGAD10 vector. Yeast two-hybrid screens were performed. Immunoprecipitation assay was performed to determine whether E6-Cdc7 interaction occurred. Cells treated with siRNA were analysed by flow cytometry.
RESULTS
We have delinated the interactions of E6 with five proteins, namely the IRF-3 (interferon regulatory factor-3), PRKCL?1 (protein kinase C-like 1), PIST (PDZ/coiled-coil domain binding gene), BARD1 (BRCA1 assocated ring domain 1), and Cdc7. The in vitro result of the interaction between E6 and Cdc7 was confirmed by immunoprecipitation experiments. Down-regulation of Cdc7 by small interfering RNA in HeLa cell lines causes an abortive S phase, leading to cell death.
CONCLUSION
We have identified the new protein of interaction with HPV E6, Cdc7 kinase. It has been implicated in S phase signaling of cell cycle and the inhibition of Cdc7 induced cell death. But, further investigation is needed to know the biologic function of Cdc7 kinase in cervical carcinogenesis.