HPV-18 E7 Interacts with Elk-1 Leading to Elevation of the Transcriptional Activity of Elk-1 in Cervical Cancer.

The human papillomavirus (HPV)-18 E7 (E7) oncoprotein is a major transforming protein that is thought to be involved in the development of cervical cancer. It is well-known that E7 stimulates tumour development by inactivating pRb. However, this alone cannot explain the various characteristics acquired by HPV infection. Therefore, we examined other molecules that could help explain the acquired cancer properties during E7-induced cancer development. Using the yeast two-hybrid (Y2H) method, we found that the Elk-1 factor, which is crucial for cell proliferation, invasion, cell survival, anti-apoptotic activity, and cancer development, binds to the E7. By determining which part of E7 binds to which domain of Elk-1 using the Y2H method, it was found that CR2 and CR3 of the E7 and parts 1-206, including the ETS-DNA domain of Elk-1, interact with each other. As a result of their interaction, the transcriptional activity of Elk-1 was increased, thereby increasing the expression of target genes EGR-1, c-fos, and E2F. Additionally, the colony forming assay revealed that overexpression of Elk-1 and E7 promotes C33A cell proliferation. We expect that the discovery of a novel E7 function as an Elk-1 activator could help explain whether the E7 has novel oncogenic activities in addition to p53 inactivation. We also expect that it will offer new methods for developing improved strategies for cervical cancer treatment.