Merkel cell polyomavirus (MCV) has been recently described as the cause for most human Merkel cell carcinomas. MCV is similar to simian virus 40 (SV40) and encodes a nuclear large T (LT) oncoprotein that is usually mutated to eliminate viral replication among tumor-derived
MCV. In search of novel cellular interactors for MCV LT, we identified the hVam6p cytoplasmic protein involved in lysosomal processing as a binding partner with MCV LT but not SV40 LT. We have shown that hVam6p binds through its clathrin heavy chain homology domain to a unique region of MCV LT adjacent to the retinoblastoma protein (pRB) binding motif. hVam6p and pRB have discrete binding sites on LT. Intriguingly, MCV LT translocates hVam6p to the nucleus, sequestering it from involvement in lysosomal trafficking. A naturally occurring, tumor-derived mutant LT (MCV350) lacking a nuclear localization signal binds hVam6p but fails to inhibit hVam6p-induced lysosomal clustering, suggesting MCV has evolved a novel mechanism to target hVam6p that may contribute to viral uncoating or egress through lysosomal processing during virus replication. In addition, we have investigated the effect of LT-hVam6p interaction on MCV virion production and viral replication. Mutation of the MCV LT-hVam6p binding site enhances encapsidated virion production, which is confirmed by both elevated subgenomic DNA synthesis and viral particle production. Remarkably, overexpression of
hVam6p reduces MCV virion production by >90%, suggesting a previously unrecognized role for this protein in regulating virus replication. Collectively, identification of novel binding partners for MCV LT has provided new insights into the mechanisms underlying the MCV lifecycle.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-06292011-103814 |
| Date | 01 August 2011 |
| Creators | Liu, Xi |
| Contributors | Ole V. Gjoerup, Patrick S. Moore, Thomas E. Smithgall, Roger Hendrix, James M. Pipas |
| Publisher | University of Pittsburgh |
| Source Sets | University of Pittsburgh |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.pitt.edu/ETD/available/etd-06292011-103814/ |
| Rights | restricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Pittsburgh or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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