Human Papillomavirus E6/E7 and Long Noncoding RNA TMPOP2 Mutually Upregulated Gene Expression in Cervical Cancer Cells

Abstract

TMPOP2 was previously suggested to be an oncogenic long noncoding RNA which is excessively expressed in cervical cancer cells and inhibits E-cadherin gene expression by recruiting transcription repressor EZH2 to the gene promoter. So far, the function and regulation of TMPOP2 in cervical cancer remain largely unknown. Herein, we found that TMPOP2 expression was correlated with human papillomavirus 16/18 (HPV16/18) E6 and E7 in cervical cancer cell lines CaSki and HeLa. Tumor suppressor p53, which is targeted for degradation by HPV16/18, was demonstrated to associate with two p53 response elements in the TMPOP2 promoter to repress the transcription of the TMPOP2 gene. Reciprocally, ectopic expression of TMPOP2 was demonstrated to sequester tumor repressor microRNAs (miRNAs) miR-375 and miR-139 which target HPV16/18 E6/E7 mRNA and resulted in an upregulation of HPV16/18 E6/E7 genes. Thereby, HPV16/18 E6/E7 and the long noncoding RNA (lncRNA) TMPOP2 form a positive feedback loop to mutually derepress gene expression in cervical cancer cells. Moreover, results of RNA sequencing and cell cycle analysis showed that knockdown of TMPOP2 impaired the expression of cell cycle genes, induced cell cycle arrest, and inhibited HeLa cell proliferation. Together, our results indicate that TMPOP2 and HPV16/18 E6/E7 mutually strengthen their expression in cervical cancer cells to enhance tumorigenic activities. IMPORTANCE Human papillomaviruses 16 and 18 (HPV16/18) are the main causative agents of cervical cancer. Viral proteins HPV16/18 E6 and E7 are constitutively expressed in cancer cells to maintain oncogenic phenotypes. Accumulating evidences suggest that HPVs are correlated with the deregulation of long noncoding RNAs (lncRNAs) in cervical cancer, although the mechanism was unexplored in most cases. TMPOP2 is a newly identified lncRNA excessively expressed in cervical cancer. However, the mechanism for the upregulation of TMPOP2 in cervical cancer cells remains largely unknown and its relationship with HPVs is still elusive. The significance of our research is in revealing the mutual upregulation of HPV16/18 E6/E7 and TMPOP2 with the molecular mechanisms explored. This study will expand our understandings of the oncogenic activities of human papillomaviruses and lncRNAs. KEYWORDS HPV E6/E7, cervical cancer, lncRNA TMPOP2, miRNAs, p53 H igh-risk human papillomaviruses (HPVs), primarily including HPV16 and HPV18, are causative agents of cervical cancer, which is one of the leading lethal female cancers worldwide. Integration of HPV DNA into the host cell genome results in the constitutive high expression of two viral oncogenes, HPV E6 and E7, under the control of cellular transcription factors. Viral protein E6 promotes p53 protein degradation FIG 4 TMPOP2 reciprocally regulated the expression of HPV E6/E7 in cervical cancer cells. (A) The efficacy of TMPOP2 knockdown in HeLa cells. (B)The protein levels of HPV18 E6/E7 were decreased following TMPOP2 knockdown. GAPDH was the protein loading control. (C) The mRNA levels of HPV1...

The Role of Long Noncoding RNAs in Human Papillomavirus-associated Pathogenesis

“…Our own experiments revealed increased EBIC expression in HPV16 E6/E7 expressing HFKs as compared to control HFKs [93] ( Figure 2B). Consistent with these results, a recent study suggested that EBIC expression was driven by E6/E7 expression, and largely due to E6 mediated TP53 degradation [39]. Interestingly, EBIC was reported to cause increased expression of HPV E6/E7 through a mechanism that involves sponging of miR-375 and miR-139, which have been previously reported to target HPV E6/E7 [112,113] (Figure 5).…”

“…Interestingly, EBIC was reported to cause increased expression of HPV E6/E7 through a mechanism that involves sponging of miR-375 and miR-139, which have been previously reported to target HPV E6/E7 [112,113] (Figure 5). EBIC depletion in the HPV18 positive HeLa cervical carcinoma line inhibited proliferation by affecting the expression of cell cycle genes such as p21 CIP1 (CDKN1A), cyclin E, and CDK2 [39].…”

Bioinformatics analysis shows that TOP2A functions as a key candidate gene in the progression of cervical cancer

“…The specific molecular mechanisms between the persistent high-risk HPV infection and the pathological process of CC are still controversial ( 5 ). Increasing evidence has shown that the abnormal expression of multiple genes are involved in the pathogenesis of CC ( 6 ). As tumorigenesis is a complex pathological process involving various genetic and epigenetic events, such as the inactivation of suppressor genes and/or the overexpression of oncogenes ( 7 ), the identification of dysregulated genes in cancer-associated pathways may highlight the molecular mechanisms underlying tumorigenesis, assisting in the development of novel strategies for treatment of CC.…”

HPV16 E6 oncoprotein‐induced upregulation of lncRNA GABPB1‐AS1 facilitates cervical cancer progression by regulating miR‐519e‐5p/Notch2 axis

“…14,15 He et al, reported that HPV16 E6/E7 and the lncRNA-TMPOP2 form a positive feedback loop to mutually strengthen oncogene expression and repress tumor repressor expression in CC. 16 A recent study identified lncRNAs expression alterations after HPV16 E6 overexpression using RNA sequencing. 17 They found that 151 lncRNAs are upregulated and 100 lncRNAs are downregulated when HPV16 E6 was expressed in keratinocytes.…”

“…E7 and lncRNAs (eg, TMPOP2) can form a positive feedback loop to mutually enhance oncogene expression and inhibit tumor repressor expression. 16 A large number of lncRNAs are abnormally expressed due to HPV16 E6 overexpression. 17 Additionally, lncRNA can function as ceRNA to regulate mRNA expression through sponging miRNAs.…”