Human Papillomavirus 16 E7 Oncoprotein Alters The Expression Profiles Of Circular RNAs In Caski Cells

Cervical cancer is one of the most common female malignancies in the world,with a high morbidity and mortality,which ranked third and fourth in the world,respectively.About 500,000 new cases and 260,000 died of this disease annually.Cervical cancer seriously affects the health of women.At present,evidences show that cervical cancer is the most closely disease associated with human papillomavirus(HPV).The high-risk HPV is regarded as the main etiologic contributor to the development of cervical cancer,of which,the high-risk types HPV16 and 18 are the most prevalent ones,accounting for more than 70%of all cervical cancer cases globally.E7 is one of the major oncoproteins encoded by HPV.It can bind to and suppress pRb through its conserved region,LXCXE motif,thus resulting in the degradation of pRb-E2F complex,activating the cell cycle related genes and promoting the synthesis of DNA cells as well as facilitating G1/S transition,thus promote the development of cervical cancer.The persistent infection of HPV is inseparable to the expression of E7.Furthermore,the continuous expression of E7 is pivotal for development and progress of cervical cancer.Therefore,it is significantly important to identify the key link and molecular target for the investigation of the pathogenesis mechanism and treatment of cervical cancer.Recently,circular RNA(circRNA),a new endogenous non-coding RNA,plays an important role in the development of human disease.After miRNA and long non-coding RNA(lncRNA),circRNA has become a promising biomarker and even therapeutic target in cancer research.CircRNAs are differently formed by back-splicing of exons or introns,lacking 5’ cap or 3’ poly A tail.The conservation,abundance and tissue specificity of the circRNA make it play a role in potentially specific markers in certain diseases.Studies have shown that the circRNA can act as a competitive endogenous RNA or miRNA sponge,can also interact with proteins,regulate gene expression and protein translation.CircRNA also has the function of regulating mRNA stability in the level of gene expression and transcription.Increasing evidence shows that circRNA plays an important role in regulating multiple diseases.In order to investigate the role of differently expressed genes in HPV16 E7 in cervical cancer,RNAi was used to knockdown E7 in Caski cells to obtain the expression profile of circRNA.526 differently expressed circRNAs(fold change≥2 or≤0.5,P<0.05)were screened by box map,scatter plot,volcanic map and heat map analysis,among which 352 were up-regulated and 174 were down-regulated.Eight differently expressed candidate circRNAs were verified by silencing E7 expression and over-expression of E7.The results showed that qRT-PCR results were consistent with the circRNA microarray.Using the online software such as Target Scan and miRBase to predict the miRNAs,five top miRNAs were obtained.GO analysis candidate circRNAs from the biological process,cellular components,molecular function,we found that circRNA mainly involved in mRNA cleavage,replication repair,regulation of protein catabolism and other processes;can act as mRNA cleavage and poly-adenylation specificity factor complexes,eukaryotic translation initiation factor 4F complex,plasma membrane and other cellular components;molecular function included RNA binding,ribosomal small sub-unit binding and helicase activity,neutral amino acid trans-membrane transport activity and so on.KEGG pathway analysis showed circRNA is mainly involved in mTOR signaling pathway,fatty acid metabolism,arginine and proline metabolism pathway.In summary,using circRNA array analysis,we first identified a subset of host circRNAs that are regulated by HPV16 E7,which showed direct evidence that the viral oncogenes have the potential to influence the expression of circRNAs likely contributing to the malignant phenotypes of cervical cancer cells.Also,our study is potentially of critical significance in uncovering the roles of circRNAs in cervical cancer,but also provides novel insights into the new potential biomarkers for diagnostic and therapeutic of cervical cancer.