ABSTRACT
BACKGROUND: High-risk HPV is a causative factor of cervical cancer. HPV DNA fragments integrate into host genome resulting in the constitutive expression of HPV genes E6 and E7 under the regulation of transcription factors, such as p300 and Tip60. Interestingly, Tip60, a factor with HAT (histone acetyl transferase) activity, represses HPV18 E6/E7 genes while another HAT p300 activates the transcription of HPV18 E6/E7. OBJECTIVE: To explore the mechanism for the opposite roles of Tip60 and p300 in the virus gene regulation, and the influence of Tip60 and p300 in histone modifications in the regulatory sequence of HPV18 genes. METHODS: Tip60 or p300 was either knocked down or overexpressed in HeLa cells. The effects on HPV E6E7 expression were determined with RT-qPCR. The association of RNA polymerase II and the enrichment of acetylated or methylated histones in HPV promoter region were measured by ChIP assays with specific antibodies. RESULTS: ChIP results showed that Tip60 and p300 differently affected the modifications of histone H3K9 and the deposition of nucleosomes in HPV18 long control region (LCR). HPV18 LCR in HeLa cells is bivalent chromatin carrying both the active histone H3K9 acetylation mark and the repressive histone H3K9 trimethylation mark, the balance is maintained by Tip60 and p300. CONCLUSION(S): Based on the roles of Tip60 and p300 in HPV gene regulation, chemical compounds targeting Tip60 or p300 are potential anti-cervical cancer drugs.
Subject(s)
DNA-Binding Proteins/genetics , Epigenesis, Genetic , Human papillomavirus 18/genetics , Lysine Acetyltransferase 5/metabolism , Oncogene Proteins, Viral/genetics , p300-CBP Transcription Factors/metabolism , DNA-Binding Proteins/metabolism , HeLa Cells , Histone Code , Humans , Lysine Acetyltransferase 5/genetics , Oncogene Proteins, Viral/metabolism , p300-CBP Transcription Factors/geneticsABSTRACT
MALAT1, a long non-coding RNA, is highly expressed in cervical cancer cells and plays an important role in the development of cervical cancer. However, the mechanism for the excessive expression of MALAT1 in cervical cancer remains unclear. High-risk HPVs are causative agents of cervical cancer and the IL-6/STAT3 signaling is closely correlated with the development of various cancers including cervical cancer. In this study, the roles of HPV18 E6/E7 and IL-6/STAT3 in the regulation of MALAT1 transcription in cervical cancer cells were investigated. It was found that HPV18 E6/E7 activated the IL-6/STAT3 signaling and, in reciprocal, IL-6/STAT3 strengthened HPV18 E6/E7 expression in HeLa cells. Both HPV18 E6/E7 and IL-6/STAT3 were involved in MALAT1 expression and they worked synergistically in the upregulation of MALAT1 gene. With luciferase reporter assays, a STAT3-binding sequence in the enhancer region of MALAT1 gene was demonstrated to be crucial for the IL-6- or STAT3-induced MALAT1 promoter activation. Taken together, our data suggest that IL-6/STAT3 mediates the HPV18 E6/E7 stimulated upregulation of MALAT1 gene in cervical cancer HeLa cells.