Faculty & Research
Molecular Biology and Pathogenesis of Human Retroviruses/ Mechanisms of Viral Carcinogenesis
My laboratory investigates the molecular and cellular processes that regulate proviral gene expression and replication of the complex retroviruses, human T-cell leukemia virus type-1 (HTLV-1) and human immunodeficiency virus type-1 (HIV-1). We are also studying how host-pathogen interactions contribute to the development of viral hematological diseases. This work involves basic and translational research with the goals of advancing our fundamental understanding of retroviral pathogenesis, elucidating novel antiviral therapeutic targets, and identifying candidate biomarkers of infectious diseases and virus-induced cancers using advanced genomic and proteomic approaches.
Both HIV-1 and HTLV-1 infect the CD4+ T-helper (Th) subpopulation of immune cells, yet, with drastically different consequences: i) HIV-1 is cytopathic and causes the progressive depletion of HIV-infected and bystander CD4+ Th-lymphocytes associated with immune-suppression and the development of acquired immune-deficiency syndrome (AIDS). ii) HTLV-1 infects and transforms CD4+ Th-cells and is the etiological agent of adult T-cell leukemia/lymphoma (ATLL), an often fatal hematological malignancy that is resistant to most anticancer treatment modalities.
HTLV-1: Our HTLV-1 research focuses on determining the roles of the retroviral nonstructural/regulatory proteins (Tax, Rex, Hbz, p12I p8I, p30II, p13II) in T-cell leukemogenesis. There are five clinically-defined stages of HTLV-induced neoplastic disease: (i) pre-ATLL, (ii) smoldering T-cell leukemia, (iii) chronic T-cell leukemia, (iv) acute T-cell leukemia, and (v) T-cell non-Hodgkin’s lymphoma. The molecular events involved in leukemic cellular transformation and disease progression remain to be completely defined. The retroviral transactivator, Tax, interacts with cellular transcription factors and deregulates signaling pathways associated with aberrant lymphoproliferation and T-cell immortalization (Harrod et al 1998; Tang et al 1998; Harrod et al 2000; Kuo et al 2000; Nicot & Harrod 2000; Johnson et al 2001; Nicot et al 2005). We are currently investigating how Tax modulates immunoregulatory pathways and retroviral gene expression through interactions with cellular transcriptional-signaling networks. We are also studying how the HTLV-1 p30II protein interacts with host factors to deregulate cellular growth/proliferation and survival during retroviral carcinogenesis. Our studies revealed a previously unknown cooperative interaction between p30II and the c-MYC oncoprotein which is frequently over-expressed in acute/lymphoma-stage ATLL lymphocytes (Awasthi et al 2005; Ko et al, in preparation). The p30II protein enhances the oncogenic potential of c-MYC and augments c-MYC-dependent transactivation and S-phase cell-cycle entry. These findings suggest that cooperation between p30II/c-MYC could contribute to ATLL tumorigenesis and the development of advanced HTLV-induced T-cell malignancies.
HIV-1: Our HIV-1 research focuses on host-pathogen interactions that control retroviral replication and transcriptional gene expression (Sharma et al 2007; Harrod et al 2003). We are particularly interested in the molecular events involved in HIV-infections of the central nervous system (CNS) and HIV neuropathogenesis (Harrod et al 2003; Wong et al 2005). HIV-1 infects CD4+ Th-lymphocytes, macrophages/monocytes (M/M) and causes AIDS, associated with the progressive loss of HIV-infected and bystander CD4+ Th-cells. Macrophages/monocytes are resistant to HIV cytotoxicity and serve as reservoirs for retroviral replication and the continuous production of infectious virus particles. HIV-infected M/M can infiltrate the CNS and cause primary encephalopathy (HIVE) and neurological diseases, such as HIV-associated dementia (HAD) and minor cognitive motor disorders (MCMD), due to HIV-infection of brain-resident cell populations (macrophages, microglia, astrocytes) and the production of neurotoxic inflammatory substances and/or retroviral proteins (Tat, Vpr, gp120). The goals of this research are to determine how neural tropic and trophic signals regulate HIV gene expression and replication in M/M, and to elucidate the pathways which promote the invasive potential of HIV-infected macrophages. These studies may lead to novel therapeutic strategies to inhibit HIV replication in the CNS and prevent the entry of HIV-infected cells into the brain.
The Laboratory: The lab is a modern BSL-2+ facility equipped with instrumentation and biosafety measures for the safe handling of infectious viral pathogens and clinical materials, including primary HTLV-infected ATLL lymphocytes to support studies of retroviral carcinogenesis and HIV-infected CNS tissues, CSF and peripheral blood samples. Since 2008, we have received three DHHS-HRSA instrumentation grants to enhance collaborative anti-infectives research. Lab equipment includes: a Zeiss AxioImager Z2 fluorescence microscope (with Apotome, 10-filtersets, and piezo-mot stage), STORM 860 phosphor-imager, AKTA Explorer FPLC/Frac 950 system, Berthold Tristar 96-well microplate reader, Stratagene Mx3005P real-time qPCR, GE Ettan-DIGE Imager with Decyder 2D/ImageMaster 2D Platinum-DIGE software, Ettan-DALTsix IPGphor3/2-dimensional gel electrophoresis system, and Shimadzu Prominence
binary gradient HPLC system for advanced proteomics applications. The lab also contains four Thermo Forma 3110 humidified CO2 incubators, two Class II laminar-flow cell/tissue culture cabinets, two Eppendorf 5810R refrigerated centrifuges, two Revco -86°C freezers, a BioRad GenePulser MXcell electroporation unit, Biorad C1000 and MJ Research thermal cyclers, GE Nanovue, IKA T25 ultra-turrax tissue homogenizer, Misonix S-4000 sonicator, Mettler Toledo XP26 microanalytical balance, an HM360 motorized microtome with stainless and tungsten carbide blades, and Histostar paraffin embedding station.
Our research is supported by the Department of Health & Human Services (DHHS-HRSA), National Cancer Institute/National Institutes of Health (NCI/NIH), and intramural grants from the University Research Council (URC). For information about positions available (e.g., postdoctoral fellow, research associate, research assistant) or training opportunities for prospective Ph.D./M.S. graduate students and undergraduates, please contact Dr. Robert Harrod (firstname.lastname@example.org).
R. Harrod (2011). Inhibiting HDACs in a preclinical model of HTLV-1-induced adult T-cell lymphoma. Leukemia Res 35:1436-1437 (invited editorial)
T. L.-N. Nguyen, de Walque, S., Veithen, E., Deckoninck, A., Martinelli, V., de Launoit, Y., Burny, A., Harrod, R., and C. Van Lint (2007). Transcriptional regulation of the bovine leukemia virus promoter by the cyclic AMP response element modulator tau isoform. J Biol Chem 282:20854-20867
A. Sharma, Awasthi, S., Harrod, C. K., Matlock, E. F., Khan, S., Xu, L., Chan, S., Yang, H., Thammavaram, C. K., Rasor, R. A., Burns, D. K., Skiest, D. J., Van Lint, C., Girard, A.-M., McGee, M., Monnat, R. J., Jr., and R. Harrod (2007). The Werner syndrome helicase is a cofactor for HIV-1 long terminal repeat transactivation and retroviral replication. J Biol Chem 282:12048-12057
S. Awasthi, Sharma, A., Wong, K., Zhang, J., Matlock, E. F., Rogers, L., Motloch, P., Takemoto, S., Taguchi, H., Cole, M. D., Luscher, B., Dittrich, O., Tagami, H.,Nakatani, Y., McGee, M., Girard, A.-M., Gaughan, L., Robson, C. N., Monnat, R. J., Jr., and R. Harrod (2005). An HTLV-1 enhancer of MYC transforming potential stabilizes MYC-TIP60 transcriptional interactions. Mol Cell Biol 25:6178-6198
C. Nicot, Harrod, R. L., Ciminale, V. and G. Franchini (2005). Human T-cell leukemia/lymphoma virus type 1 nonstructural genes and their functions. Oncogene 24:6026-6034
K. Wong, Sharma, A., Awasthi, S., Matlock, E. F., Rogers, L., Van Lint, C., Skiest, D. J., Burns, D. K., and R. Harrod (2005). HIV-1 Tat interactions with p300 and PCAF transcriptional coactivators inhibit histone acetylation and neurotrophin-signaling through CREB. J Biol Chem 280:9390-9399
K. Wong, Zhang, J., Awasthi, S., Sharma, A., Rogers, L., Matlock, E. F., Van Lint, C., Karpova, T., McNally, J., and R. Harrod (2004). Nerve growth factor receptor-signaling induces histone acetyltransferase domain-dependent nuclear translocation of p300/CREB-binding protein-associated factor and hGCN5 acetyltransferases. J Biol Chem 279:55667-55674
R. Harrod, Nacsa, J., Van Lint, C., Hansen, J., Karpova, T., McNally, J., and G. Franchini (2003). HIV-1 Tat/co-activator acetyltransferase interactions Inhibit p53K320-acetylation and p53-responsive transcription. J Biol Chem 278:12310-12318
Z. Hel, Johnson, J. M., Tryniszewska, E., Tsai, W. P., Harrod, R., Fullen, J., Tartaglia, J., and G. Franchini (2002). A novel chimeric Rev, Tat, and Nef antigen as a component of an SIV/HIV vaccine. Vaccine 20:3171-3186
Z. Hel., Tryniszewska, E., Tsai, W. P., Johnson, J. M., Harrod, R., Fullen, J., Kalyanaraman, V. S., Altman, J. D., McNally, J., Karpova, T., Felber, B. K., Tartaglia, J., and G. Franchini (2002). Design and in vivo immunogenicity of a polyvalent vaccine based on SIVmac regulatory genes. DNA and Cell Biol 21:619-626
J. M. Johnson, Harrod, R., and G. Franchini (2001). Molecular biology and pathogenesis of the human T-cell leukaemia/lymphotropic virus type-1 (HTLV-1). Int J Exp Path 82: 135-147
C. Nicot and R. Harrod (2000). Distinct p300-responsive mechanisms promote caspase-dependent apoptosis by HTLV-1 Tax. Mol Cell Biol 20:8580-8589
Kuo, Y. L., Tang, Y.,
Y. L. Kuo, Tang, Y., Harrod, R., Cai, P., and C. Z. Giam (2000). Kinase-inducible domain-like region of HTLV type 1 Tax is important for NF-kappaB activation. AIDS Research and Human Retroviruses 16:1607-1612
Y. Yao, Kuo, Y. L., Wang, L. C., Harrod R., Tang, Y., Cai, P., Harrington, W. J., Boros, I., Shih, H. M., and C. Z. Giam (2000). Mechanisms of action of HTLV-1 Tax. Leukemia 14:535
R. Harrod, Tang, Y., Nicot, C., Lu, H. S., Vassilev, A., Nakatani, Y., and C. Z. Giam (1998). An exposed KID-like domain in HTLV-1 Tax is responsible for the recruitment of co-activators CBP/p300. Mol Cell Biol 18:5052-5061
Y. Tang, Tie, F., Boros,
R. Harrod and P. S. Lovett (1997). Leader peptides of inducible chloramphenicol resistance genes from Gram-positive and Gram-negative bacteria bind to yeast and Archaea large subunit rRNA. Nucl Acids Res 25:1720-1726
R. Harrod and P. S. Lovett (1995). Peptide inhibitors of peptidyl transferase alter the conformation of domains IV and V of large subunit rRNA: A model for nascent peptide control of translation. Proc Nat'l Acad Sci, USA 92:8650-8654
Z. Gu, Harrod, R., Rogers, E. J., and P. S. Lovett (1994). Properties of a pentapeptide inhibitor of peptidyltransferase that is essential for cat gene regulation by translation attenuation. J Bacteriol 176:6238-6244
Z. Gu, Harrod, R., Rogers, E. J., and P. S. Lovett (1994). Anti-peptidyl transferase leader peptides of attenuation-regulated chloramphenicol-resistance genes. Proc Nat'l Acad Sci, USA 91:5612-5616
R. Harrod, Gu, Z., and P. S. Lovett (1994). Analysis of the secondary structure that negatively regulates inducible cat translation by use of chemical probing and mutagenesis. Gene 140:79-83
Awards and Honors
Membership in Professional Societies