Bio

Honors & Awards


  • Ruth L. Kirschstein National Research Service Award, National Cancer Institute (2012-2015)

Professional Education


  • Doctor of Philosophy, University of Connecticut (2010)

Stanford Advisors


Research & Scholarship

Current Research and Scholarly Interests


protein quality control
ubiquitin-proteasome system
protein misfolding in cancer

Publications

Journal Articles


  • ATR and ATRIP Are Recruited to Herpes Simplex Virus Type 1 Replication Compartments Even though ATR Signaling Is Disabled JOURNAL OF VIROLOGY Mohni, K. N., Livingston, C. M., Cortez, D., Weller, S. K. 2010; 84 (23): 12152-12164

    Abstract

    Although the herpes simplex virus type 1 (HSV-1) genome might be expected to induce a DNA damage response, the ATR kinase is not activated in infected cells. We previously proposed that spatial uncoupling of ATR from its interaction partner, ATRIP, could be the basis for inactivation of the ATR kinase in infected cells; however, we now show that ATR and ATRIP are in fact both recruited to HSV-1 replication compartments and can be coimmunoprecipitated from infected-cell lysates. ATRIP and replication protein A (RPA) are recruited to the earliest detectable prereplicative sites, stage II microfoci. In a normal cellular DNA damage response, ATR/ATRIP are recruited to stretches of RPA-coated single-stranded DNA in an RPA- and kinase-dependent manner, resulting in the phosphorylation of RPA by ATR in damage foci. In contrast, in HSV-1-infected cells, RPA is not phosphorylated, and endogenous phosphorylated RPA is excluded from stage II microfoci; in addition, the recruitment of ATR/ATRIP is independent of RPA and the kinase activity of ATR. Furthermore, we show that ATR/ATRIP play a beneficial role in viral gene expression and virus production. Although ICP0 has been shown to be important for partial inactivation of other cellular DNA repair pathways, we show that ICP0 is not responsible for the inactivation of ATR signaling and, furthermore, that neither ATR nor ATRIP is a target of ICP0 degradation. Thus, ATR and ATRIP may function outside the context of the canonical ATR damage signaling pathway during HSV-1 infection to participate in the viral life cycle.

    View details for DOI 10.1128/JVI.01643-10

    View details for Web of Science ID 000283799500005

    View details for PubMedID 20861269

  • Herpes Simplex Virus Type 1 Immediate-Early Protein ICP22 Is Required for VICE Domain Formation during Productive Viral Infection JOURNAL OF VIROLOGY Bastian, T. W., Livingston, C. M., Weller, S. K., Rice, S. A. 2010; 84 (5): 2384-2394

    Abstract

    During productive infection, herpes simplex virus type 1 (HSV-1) induces the formation of discrete nuclear foci containing cellular chaperone proteins, proteasomal components, and ubiquitinated proteins. These structures are known as VICE domains and are hypothesized to play an important role in protein turnover and nuclear remodeling in HSV-1-infected cells. Here we show that VICE domain formation in Vero and other cells requires the HSV-1 immediate-early protein ICP22. Since ICP22 null mutants replicate efficiently in Vero cells despite being unable to induce VICE domain formation, it can be concluded that VICE domain formation is not essential for HSV-1 productive infection. However, our findings do not exclude the possibility that VICE domain formation is required for viral replication in cells that are nonpermissive for ICP22 mutants. Our studies also show that ICP22 itself localizes to VICE domains, suggesting that it could play a role in forming these structures. Consistent with this, we found that ICP22 expression in transfected cells is sufficient to reorganize the VICE domain component Hsc70 into nuclear inclusion bodies that resemble VICE domains. An N-terminal segment of ICP22, corresponding to residues 1 to 146, is critical for VICE domain formation in infected cells and Hsc70 reorganization in transfected cells. We previously found that this portion of the protein is dispensable for ICP22's effects on RNA polymerase II phosphorylation. Thus, ICP22 mediates two distinct regulatory activities that both modify important components of the host cell nucleus.

    View details for DOI 10.1128/JVI.01686-09

    View details for Web of Science ID 000274330300018

    View details for PubMedID 20032172

  • Virus-Induced Chaperone-Enriched (VICE) Domains Function as Nuclear Protein Quality Control Centers during HSV-1 Infection PLOS PATHOGENS Livingston, C. M., Ifrim, M. F., Cowan, A. E., Weller, S. K. 2009; 5 (10)

    Abstract

    Virus-Induced Chaperone-Enriched (VICE) domains form adjacent to nuclear viral replication compartments (RC) during the early stages of HSV-1 infection. Between 2 and 3 hours post infection at a MOI of 10, host protein quality control machinery such as molecular chaperones (e.g. Hsc70), the 20S proteasome and ubiquitin are reorganized from a diffuse nuclear distribution pattern to sequestration in VICE domains. The observation that VICE domains contain putative misfolded proteins suggests that they may be similar to nuclear inclusion bodies that form under conditions in which the protein quality control machinery is overwhelmed by the presence of misfolded proteins. The detection of Hsc70 in VICE domains, but not in nuclear inclusion bodies, indicates that Hsc70 is specifically reorganized by HSV-1 infection. We hypothesize that HSV-1 infection induces the formation of nuclear protein quality control centers to remodel or degrade aberrant nuclear proteins that would otherwise interfere with productive infection. Detection of proteolytic activity in VICE domains suggests that substrates may be degraded by the 20S proteasome in VICE domains. FRAP analysis reveals that GFP-Hsc70 is dynamically associated with VICE domains, suggesting a role for Hsc70 in scanning the infected nucleus for misfolded proteins. During 42 degrees C heat shock, Hsc70 is redistributed from VICE domains into RC perhaps to remodel viral replication and regulatory proteins that have become insoluble in these compartments. The experiments presented in this paper suggest that VICE domains are nuclear protein quality control centers that are modified by HSV-1 to promote productive infection.

    View details for DOI 10.1371/journal.ppat.1000619

    View details for Web of Science ID 000272033300024

    View details for PubMedID 19816571

  • Oligomerization of ICP4 and rearrangement of heat shock proteins may be important for herpes simplex virus type 1 prereplicative site formation JOURNAL OF VIROLOGY Livingston, C. M., Deluca, N. A., Wilkinson, D. E., Weller, S. K. 2008; 82 (13): 6324-6336

    Abstract

    Herpes simplex virus type 1 (HSV-1) DNA replication occurs in replication compartments that form in the nucleus by an ordered process involving a series of protein scaffold intermediates. Following entry of viral genomes into the nucleus, nucleoprotein complexes containing ICP4 can be detected at a position adjacent to nuclear domain 10 (ND10)-like bodies. ND10s are then disrupted by the viral E3 ubiquitin ligase ICP0. We have previously reported that after the dissociation of ND10-like bodies, ICP8 could be observed in a diffuse staining pattern; however, using more sensitive staining methods, we now report that in addition to diffuse staining, ICP8 can be detected in tiny foci adjacent to ICP4 foci. ICP8 microfoci contain UL9 and components of the helicase-primase complex. HSV infection also results in the reorganization of the heat shock cognate protein 70 (Hsc70) and the 20S proteasome into virus-induced chaperone-enriched (VICE) domains. In this report we show that VICE domains are distinct but adjacent to the ICP4 nucleoprotein complexes and the ICP8 microfoci. In cells infected with an ICP4 mutant virus encoding a mutant protein that cannot oligomerize on DNA, ICP8 microfoci are not detected; however, VICE domains could still be formed. These results suggest that oligomerization of ICP4 on viral DNA may be essential for the formation of ICP8 microfoci but not for the reorganization of host cell chaperones into VICE domains.

    View details for DOI 10.1128/JVI.00455-08

    View details for Web of Science ID 000256947300022

    View details for PubMedID 18434395

  • A mutation in the human herpes simplex virus type 1 UL52 zinc finger motif results in defective primase activity but can recruit viral polymerase and support viral replication efficiently JOURNAL OF VIROLOGY Chen, Y., Livingston, C. M., Carrington-Lawrence, S. D., Bai, P., Weller, S. K. 2007; 81 (16): 8742-8751

    Abstract

    Herpes simplex virus type 1 (HSV-1) encodes a heterotrimeric helicase/primase complex consisting of UL5, UL8, and UL52. UL5 contains conserved helicase motifs, while UL52 contains conserved primase motifs, including a zinc finger motif. Although HSV-1 and HSV-2 UL52s contain a leucine residue at position 986, most other herpesvirus primase homologues contain a phenylalanine at this position. We constructed an HSV-1 UL52 L986F mutation and found that it can complement a UL52 null virus more efficiently than the wild type (WT). We thus predicted that the UL5/8/52 complex containing the L986F mutation might possess increased primase activity; however, it exhibited only 25% of the WT level of primase activity. Interestingly, the mutant complex displayed elevated levels of DNA binding and single-stranded DNA-dependent ATPase and helicase activities. This result confirms a complex interdependence between the helicase and primase subunits. We previously showed that primase-defective mutants failed to recruit the polymerase catalytic subunit UL30 to prereplicative sites, suggesting that an active primase, or primer synthesis, is required for polymerase recruitment. Although L986F exhibits decreased primase activity, it can support efficient replication and recruit UL30 efficiently to replication compartments, indicating that a partially active primase is capable of recruiting polymerase. Extraction with detergents prior to fixation can extract nucleosolic proteins but not proteins bound to chromatin or the nuclear matrix. We showed that UL30 was extracted from replication compartments while UL42 remained bound, suggesting that UL30 may be tethered to the replication fork by protein-protein interactions.

    View details for DOI 10.1128/JVI.00174-07

    View details for Web of Science ID 000248649100037

    View details for PubMedID 17553899

  • Activation of porcine cytomegalovirus, but not porcine lymphotropic herpesvirus, in pig-to-baboon xenotransplantation JOURNAL OF INFECTIOUS DISEASES Mueller, N. J., Livingston, C., Knosalla, C., Barth, R. N., Yamamoto, S., Gollackner, B., Dor, F. J., Buhler, L., Sachs, D. H., Yamada, K., Cooper, D. K., Fishman, J. A. 2004; 189 (9): 1628-1633

    Abstract

    Tissue-invasive disease due to porcine cytomegalovirus (PCMV) has been demonstrated after pig-to-baboon solid-organ xenotransplantation. Porcine lymphotropic herpesvirus (PLHV)-1 is associated with B cell proliferation and posttransplant lymphoproliferative disorder after allogeneic bone marrow transplantation in swine but has not been observed in pig-to-primate xenotransplantation. Activation of PCMV and PLHV-1 was investigated in 22 pig-to-baboon xenotransplants by use of quantitative polymerase chain reaction. PCMV was found in all xenografts; increased viral replication occurred in 68% of xenografts during immunosuppression. PLHV-1 was found in 12 xenografts (55%); no increases in viral replication occurred during immunosuppression. Control immunosuppressed swine coinfected with PCMV and PLHV-1 had activation of PCMV but not PLHV-1. PCMV, but not PLHV-1, is activated in solid-organ xenotransplantation.

    View details for Web of Science ID 000220951300011

    View details for PubMedID 15116299

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