LncRNA MALAT1 was regulated by HPV16 E7 independently of pRB in cervical cancer cells.

Abstract

High-risk human papillomavirus (HPV) infection was one of the first step in the process of carcinogenesis in cervical cancers. The expression of viral oncoprotein E7 was essential in this process by inactivating the tumor suppressor proteins RB, in addition to interacting with other host proteins. LncRNA MALAT1 was found to be altered in human cervical cancer tissues, suggesting an important role in tumorigenesis. Moreover, MALAT1 was also overexpressed in HPV16 positive cervical cancer cell lines in an HPV16 E7 dependent manner. To explore the mechanism of E7 involved in MALAT1 up-regulation, the deletion mutant E7∆N and E7∆C were constructed to test the functional domain of E7 for MALAT1 regulation. ChIP, EMSA and UV crosslink were performed to detect the interaction between E7 and MALAT1 promoter. E7 and E7∆N mutant were observed that could bind with MALAT1 promoter directly and interacted with SP1 to form triple complex. E7-SP1 interaction contributed to the transcription activation of MALAT1 promoter. E7 and E7∆N also could promote cell proliferation, invasion, and migration, and the stimulating effect could be reversed by siMALAT1. Here we showed that HPV16 E7 as well as E7∆N could associate with SP1 and bound directly to MALAT1 promoter in vitro and in vivo. This function way of E7 was independent of pRB in cervical cancer cells. To our knowledge, this was the first reported function model for E7 as transcription activator to directly bind to the target promoter.