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IDENTIFICATION OF HUMAN VAM6P AS A NOVELCELLULAR INTERACTOR FOR MERKEL CELL POLYOMAVIRUS LARGE T ANTIGEN

Liu, Xi (2011) IDENTIFICATION OF HUMAN VAM6P AS A NOVELCELLULAR INTERACTOR FOR MERKEL CELL POLYOMAVIRUS LARGE T ANTIGEN. Doctoral Dissertation, University of Pittsburgh.

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    Abstract

    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-derivedMCV. 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 ofhVam6p 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.


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    Item Type: University of Pittsburgh ETD
    Creators/Authors:
    CreatorsEmailORCID
    Liu, Xixil48@pitt.edu
    ETD Committee:
    ETD Committee TypeCommittee MemberEmailORCID
    Committee ChairMoore, Patrick S.
    Committee MemberPipas, James M.
    Committee MemberGjoerup, Ole V.
    Committee MemberHendrix, Roger
    Committee MemberSmithgall, Thomas E.
    Title: IDENTIFICATION OF HUMAN VAM6P AS A NOVELCELLULAR INTERACTOR FOR MERKEL CELL POLYOMAVIRUS LARGE T ANTIGEN
    Status: Unpublished
    Abstract: 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-derivedMCV. 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 ofhVam6p 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.
    Date: 01 August 2011
    Date Type: Completion
    Defense Date: 15 June 2011
    Approval Date: 01 August 2011
    Submission Date: 29 June 2011
    Access Restriction: 5 year -- Restrict access to University of Pittsburgh for a period of 5 years.
    Patent pending: No
    Institution: University of Pittsburgh
    Thesis Type: Doctoral Dissertation
    Refereed: Yes
    Degree: PhD - Doctor of Philosophy
    URN: etd-06292011-103814
    Uncontrolled Keywords: lysosomal trafficking; virion production
    Schools and Programs: School of Medicine > Integrative Molecular Biology
    Date Deposited: 10 Nov 2011 14:49
    Last Modified: 19 Jun 2012 13:53
    Other ID: http://etd.library.pitt.edu/ETD/available/etd-06292011-103814/, etd-06292011-103814

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