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Zhi-Ming Zheng, M.D., Ph.D.
Viral RNA Splicing and Oncogenesis
Zheng first identified RNA cis-elements in regulation of alternative RNA splicing in papillmavirus in 1996 and has been studying protein-RNA interactions and their consequences in various infections with tumorviruses, including high-risk human papillomaviruses and Kaposi sarcoma-associated herpesvirus. This study aims to understand how RNA splicing and small regulatory RNAs regulate the expression of viral and host genes in viral carcinogenesis. The long-term goal is to develop a series of therapeutic approaches to control viral or cellular gene expression for cancer treatment and to identify biomarkers for clinical diagnosis and prognosis.
1. Papillomavirus infection and viral gene expression.
Human papillomavirus type 16 (HPV16) or 18 (HPV18) infection, acquired primarily via sexual transmission, is widely recognized as a leading cause of cervical and anal cancer. Persistent infection with oncogenic or high-risk HPVs in other tissues also leads to the development of cancers. Two viral oncoproteins, E6 and E7, of oncogenic HPVs are involved in cervical carcinogenesis and are known to destabilize cellular tumor suppressor proteins and to induce aberrant expression of a subset of oncogenic and tumor-suppressive miRNAs. In HPV16 and HPV18, E6 and E7 are transcribed as a single bicistronic E6E7 RNA bearing 3 exons and 2 introns, with the intron 1 in the E6 coding region. Splicing of the intron 1 in E6E7 pre-mRNA disrupts the E6 ORF, but is required to reinitiate translation of the E7 ORF downstream. Thus, RNA splicing regulates the production of viral E6 and E7. We found that cellular RNA splicing factors, including SRSF3 (SRp20), control virus early-to-late switch through binding to viral RNA cis-elements. We demonstrated that SRp20 is a proto-oncogene essential for cell proliferation. When overexpressed, it induces tumor formation. Together, the HPV infection-induced degradation of host tumor suppressive proteins, aberrant expression of oncogenic and tumor-suppressive miRNAs, and enhancement of SRp20 expression could be three distinguishable mechanisms leading to the development of cervical cancer.
2. KSHV Gene expression and post-transcriptional regulation.
KSHV is a lymphotropic DNA tumor virus that induces Kaposi sarcoma (KS), primary effusion lymphoma (PEL) or body cavity-based B-cell lymphoma, and multicentric Castleman disease (MCD). Among those malignancies, KS occurs frequently in the patients infected with HIV. PEL and MCD feature the increased levels of cytokines (IL6 and IL10). Latent KSHV infection in KS lesions and PEL-derived B cells can be reactivated as lytic KSHV infection by various stress conditions or inflammation. In KSHV lytic infection, a viral lytic gene ORF57 encodes a multifunctional, caspase-7 sensitive protein to regulate the expression of a subset of viral lytic genes at the posttranscriptional level. We demonstrated that ORF57 carries out this function by binding to RNA and interacting with cellular RNA-binding proteins. ORF57 functions as a viral splicing factor and promotes RNA splicing by interacting with the spliceosomal machinery and by attenuation of SRSF3 activities. ORF57 binds to and stabilizes viral RNAs by interaction with host RNA capping, export, and polyadenylation factors. ORF57 promotes IL6 expression by interrupting miRNA-mediated RNA instability and translational repression.
Our lab has extensive collaborations on various projects with many investigators. Our current collaborators are Adrian Krainer of Cold Spring Harbor Laboratory, Craig Meyers of Pennsylvania State University, Louise Chow of University of Alabama at Birmingham, Thomas Tuschl of Rockefeller University and Robert Yarchoan, Michael Kruhlak, J. Philip McCoy, Jr., Chuxia Deng, Jun Zhu, Curtis Harris, and Mikhail Kashlev of NIH.
This page was last updated on 7/6/2014.