Zhi-Ming Zheng

HPV oncogenes expressed from only one of multiple integrated HPV DNA copies drive clonal cell expansion in cervical cancer

ABSTRACT The integration of HPV DNA into human chromosomes plays a pivotal role in the onset of papillomavirus-related cancers. HPV DNA integration often occurs by linearizing the viral DNA in the E1/E2 region, resulting in the loss of a critical viral early polyadenylation signal (PAS), which is essential for the polyadenylation of the E6E7 bicistronic transcripts and for the expression of the viral E6 and E7 oncogenes. Here, we provide compelling evidence that, despite the presence of numerous integrated viral DNA copies, virus-host fusion transcripts originate from only a single integrated HPV DNA in HPV16 and HPV18 cervical cancers and cervical cancer-derived cell lines. The host genomic elements neighboring the integrated HPV DNA are critical for the efficient expression of the viral oncogenes that leads to clonal cell expansion. The fusion RNAs that are produced use a host RNA polyadenylation signal downstream of the integration site, and almost all involve splicing to host sequences. In cell culture, siRNAs specifically targeting the host portion of the virus-host fusion transcripts effectively silenced viral E6 and E7 expression. This, in turn, inhibited cell growth and promoted cell senescence in HPV16+ CaSki and HPV18+ HeLa cells. Showing that HPV E6 and E7 expression from a single integration site is instrumental in clonal cell expansion sheds new light on the mechanisms of HPV-induced carcinogenesis and could be used for the development of precision medicine tailored to combat HPV-related malignancies. IMPORTANCE Persistent oncogenic HPV infections lead to viral DNA integration into the human genome and the development of cervical, anogenital, and oropharyngeal cancers. The expression of the viral E6 and E7 oncogenes plays a key role in cell transformation and tumorigenesis. However, how E6 and E7 could be expressed from the integrated viral DNA which often lacks a viral polyadenylation signal in the cancer cells remains unknown. By analyzing the integrated HPV DNA sites and expressed HPV RNAs in cervical cancer tissues and cell lines, we show that HPV oncogenes are expressed from only one of multiple chromosomal HPV DNA integrated copies. A host polyadenylation signal downstream of the integrated viral DNA is used for polyadenylation and stabilization of the virus-host chimeric RNAs, making the oncogenic transcripts targetable by siRNAs. This observation provides further understanding of the tumorigenic mechanism of HPV integration and suggests possible therapeutic strategies for the development of precision medicine for HPV cancers.

Ecdysoneless Protein Regulates Viral and Cellular mRNA Splicing to Promote Cervical Oncogenesis

Abstract High-risk human papillomaviruses (HPV), exemplified by HPV16/18, are causally linked to human cancers of the anogenital tract, skin, and upper aerodigestive tract. Previously, we identified Ecdysoneless (ECD) protein, the human homolog of the Drosophila ecdysoneless gene, as a novel HPV16 E6–interacting protein. Here, we show that ECD, through its C-terminal region, selectively binds to high-risk but not to low-risk HPV E6 proteins. We demonstrate that ECD is overexpressed in cervical and head and neck squamous cell carcinoma (HNSCC) cell lines as well as in tumor tissues. Using The Cancer Genome Atlas dataset, we show that ECD mRNA overexpression predicts shorter survival in patients with cervical and HNSCC. We demonstrate that ECD knockdown in cervical cancer cell lines led to impaired oncogenic behavior, and ECD co-overexpression with E7 immortalized primary human keratinocytes. RNA-sequencing analyses of SiHa cells upon ECD knockdown showed to aberrations in E6/E7 RNA splicing, as well as RNA splicing of several HPV oncogenesis–linked cellular genes, including splicing of components of mRNA splicing machinery itself. Taken together, our results support a novel role of ECD in viral and cellular mRNA splicing to support HPV-driven oncogenesis. Implications: This study links ECD overexpression to poor prognosis and shorter survival in HNSCC and cervical cancers and identifies a critical role of ECD in cervical oncogenesis through regulation of viral and cellular mRNA splicing.

Human Papillomavirus Type 16 Circular RNA Is Barely Detectable for the Claimed Biological Activity

RNA back-splicing is a rare splicing event accounting for <1% of canonical RNA splicing and, thus, is thought to have little or no biological significance. Recently, circular RNAs (circRNAs) from RNA back-splicing have been found widely in cells and tissues and may have a role in modulating RNA transcription, splicing, and interference and antiviral innate immunity.

The long noncoding RNA lnc-FANCI-2 intrinsically restricts RAS signaling in human papillomavirus type 16-infected cervical cancer cells

Increased expression of lnc-FANCI-2, a newly discovered long noncoding RNA, is associated with cervical lesion progression from cervical intraepithelial neoplasia stage 1 (CIN1, low grade), CIN2–3 (high grade), to cervical cancer. Viral oncoprotein E7 of high-risk human papillomaviruses (HR-HPVs) and host transcription factor YY1 are two major factors promoting lnc-FANCI-2 expression. Using CRISPR-Cas9 technology, we knocked out the expression of lnc-FANCI-2 in the HPV16-positive cervical cancer cell line, CaSki cells. The selected knockout (KO) single-cell clones displayed altered cell morphology and proliferation with changes of cellular soluble receptors, but normal HPV16 E6 and E7 expression. Relative to the parental cells, lnc-FANCI-2 KO cells exhibited significantly increased RAS signaling and epithelial-mesenchymal transition, but decreased response to IFN signaling, along with increased p-Akt and p-Erk1/2 (two RAS signaling effectors), IGFBP3, MCAM, VIM, and CCND2 (cyclin D2) and decreased expression of RAC3. lnc-FANCI-2 in CaSki interacts with cellular proteins H13, HNRH1, K1H1, MAP4K4, and RNPS1. MAP4K4 knockdown led to enhance the expression of p-Erk1/2 and p-Akt. High lnc-FANCI-2 and low MCAM levels in cervical cancer tissues were found to be associated with patients’ survival. A key function of lnc-FANCI-2 intrinsically regulates RAS signaling to impact cervical lesion progression and cervical cancer prognosis.