Marc Johnson, PhD

Associate Professor

Molecular Microbiology & Immunology


(573) 882-1519

Fields of Interest

  • Retrovirus assembly


  • Ph.D. 1999, Oregon State University

Research Statement

Retrovirus assembly

Retroviral assembly is an elegant biological process that involves multiple viral and cellular actors from diverse locations within the cell converging at defined assembly sites to create and facilitate the egress of an infectious viral particle. I utilize the model retrovirus HIV-1 to study how the basic viral components (proteins, glycoproteins, and RNAs) are targeted to viral assembly sites and how cellular processes are usurped to aid in this process. A combination of novel fluorescence and scanning electron microscopy techniques are utilized to better understand how these complex processes take place.

The focus of my research is understanding how viruses put themselves together. Most enveloped RNA viruses (which includes HIV, ebola, rabies, measles, and influenza, to name a few) are composed of the same basic ingredients: a viral RNA genome, viral structural proteins, and viral trans-membrane targeting/fusion glycoproteins. During an infection, these diverse viral components elegantly converge at a predetermined cellular location to assemble into a new virus that buds away from its host cell. This process is quite precise as most viruses contain a set number of viral genomes, a specific type of cellular lipid bi-layer, and very few cellular RNAs or proteins. Although researchers have made tremendous progress in recent years towards understanding what cellular processes are usurped by viruses to facility the process of viral release, very little is know about the early events that lead to viral assembly.

I primarily use retroviruses to study viral assembly and my work focuses on three model retroviruses: human immunodeficiency virus (HIV, the causative agent of AIDS), murine leukemia virus (MLV, the primary retroviral vector used in gene therapy), and Rous sarcoma virus (RSV, the classic model retrovirus). Retroviruses express a single structural protein, Gag, which by itself can assemble into non-infectious virus particles.


The assembly of Gag into a virus particle can be viewed at high magnifications in fixed cells using scanning or transmission electron microscopy (SEM and TEM) or at lower magnifications in live cells using fluorescently-tagged Gag proteins. I have developed a correlative system that combines both of these techniques by first imaging cells in real time by fluorescence microscopy and then imaging the exact same cells by SEM (Fig1), yielding a more comprehensive view of viral assembly. Using this technique I can begin to quantitatively dissect the pathway followed by the Gag as it assembles into a virus.

research_johnson2 TA second focus in viral assembly is understanding how viruses target their cytoplasmic structural proteins to the same assembly sites as their trans-membrane targeting/fusion glycoproteins. It has long been observed that enveloped viruses readily incorporate foreign viral glycoproteins, but exclude foreign cellular glycoproteins. This selective incorporation occurs even when the viral glycoproteins are entirely unrelated and contain no sequence similarity.

These observations have led to the theory that viruses utilize a common glycoprotein targeting pathway/mechanism to drive viral incorporation. I have developed a method for observing viral assembly sites on a cell using standard secondary electron SEM while simultaneously viewing the distribution of gold labeled viral glycoproteins using backscatter SEM. Using this technique I have been able to show that there is a 50-100 fold enrichment of viral glycoproteins at viral assembly sites regardless of whether the structural proteins and glycoproteins are derived from the same virus (Fig 2A and B). By comparing similar proteins that are targeted to or excluded from budding sites, I now have a system to tease apart the requirements for and mechanisms of glycoprotein targeting.

Selected Publications

  1. Lange, M.J., Sharma, T.K., Whatley, A.S., Landon, L.A., Tempesta, M.A., Johnson, M.C., and Burke, D.H. 2012. Robust suppression of HIV replication by intracellularly expressed RNA aptamers to reversetranscriptase is independent of ribozyme processing. Mol Ther. 2012 Sep 4. doi: 10.1038/mt.2012.158. [Epub ahead of print]
  2. Ndongwe, T.P., Adedeji, A.O., Michailidis, E., Ong, Y.T., Hachiya, A., Marchand, B., Ryan, E.M., Rai, D.K., Kirby, K.A., Whatley, A.S., Burke, D.H., Johnson, M.C., Ding, S., Zheng, Y-M., Liu, S-L., Kodama, E-I., Delviks-Frankenberry, K.A., Pathak, V.K., Mitsuya, H., Parniak, M.A., Singh, K., and Sarafianos, S.G. 2012. Biochemical, Inhibition, and Resistance Studies of Xenotropic Murine Leukemia Virus-Related Virus Reverse Transcriptase. Nucleic Acids Res. 40:345-359 (accepted August 2011). Supplemental.
  3. Baluyot, M.F., Grosse, S.A., Lyddon T.D., Janaka, S.K., and Johnson, M.C. 2012. CRM1-dependent trafficking of retroviral Gag proteins revisited. J. Virology. 2012 Apr;86(8):4696-700. Epub 2012 Feb 8.
  4. Janaka, S.K, Lucas, T.M., and Johnson, M.C. 2011. Sequences in gibbon ape leukemia virus envelope that confer sensitivity to HIV-1 accessory protein Vpu. J Virology 85(22):11945.
  5. Zhang, F., Zang, T., Wilson, S.J., Johnson, M.C., and Bieniasz, P.D. 2011. Clathrin facilitates the morphogenesis of retrovirus particles. PLoS Pathog. 7(6):e1002119. Epub 2011 Jun 30.
  6. Johnson, M.C. 2011. Mechanisms for Env Glycoprotein Acquisition by Retroviruses. (Review) AIDS Research and Human Retroviruses 27(3):239-47. Epub 2011 Feb 22.
  7. Lucas, T., Lyddon, T. D., Gross, S.A., and Johnson, M.C. 2010. Two distinct mechanisms regulate recruitment of murine leukemia virus envelope protein to retroviral assembly sites. Virology 405(2):548-55. Epub 2010 Jul 23.
  8. Dilley K.A., Gregory D.A., Johnson M.C., and Vogt, V.M. 2010. An LYPSL late domain in the Gag protein contributes to the efficient release of Rous sarcoma virus. J of Virology 84(13):6276-87. Epub 2010 Apr 14.
  9. Lucas T.M., Lyddon T.D., Cannon P.M., and Johnson M.C. 2010. The pseudotyping incompatibilitybetween HIV-1 and GaLV Env is modulated by Vpu. J Virology 84(6):2666-74. Epub 2009 Dec 30.
  10. Perez-Caballero D., Zang T., Ebrahimi A., McNatt M.W., Gregory D.A., Johnson M.C., and Bieniasz P.D. 2009. Tetherin inhibits HIV-1 release by directly tethering virions to cells. Cell 139(3):499-511.
  11. Zhang F., Wilson S.J., Landford W.C., Virgen B., Gregory D., Johnson M.C., Munch J., Kirchhoff F., Bieniasz P.D., and Hatziioannou T. 2009. Nef Proteins from Simian Immunodeficiency Viruses Are Tetherin Antagonists. Cell Host Microbe 6(1):54-67. Epub 2009 Jun 4.
  12. Jorgenson, R.L., Vogt, V.M. and Johnson, M.C. 2009. Foreign glycoproteins are robustly recruited to virus assembly sites during pseudotyping. J Virology 83(9):4060-7. Epub 2009 Feb 18.
  13. Carlson L.A., Briggs J.A., Glass B., Riches J.D., Simon M.N., Johnson M.C., Müller B., Grünewald K., and Kräusslich H.G. 2008. Three-dimensional analysis of budding sites and released virus suggests a revised model for HIV-1 morphogenesis. Cell Host Microbe 4(6):592-9.
  14. Keller, P.W., Johnson, M.C., and Vogt, V.M. 2008. Mutations in SP and adjoining sequences in Rous sarcoma virus Gag lead to tubular budding. J Virology 82(14):6788-97. Epub 2009 Feb 18.
  15. Van Damme, N., Goff, D., Katsura, C., Jorgenson, R.L., Mitchell, R., Johnson, M.C., Stephens, E.B., and Guatelli, J. 2008. The interferon-induced protein BST-2/CD317 restricts release of virions from infected cells and is down-regulated from the cell surface by HIV-1 Vpu. Cell Host Microbe 3(4):245-52. Epub 2008 Mar 13.
  16. Capkovic, K.L., Stevenson, S., Johnson, M.C., Thelen, J.J., and Cornelison, D.D. 2008. Neural cell adhesion molecule (NCAM) marks adult myogenic cells committed to differentiation. Exp Cell Res 314(7):1553-65. Epub 2008 Feb 9.
  17. Zhadina, M., McClure, M.O., Johnson, M. C., and Bieniasz, P. D. 2007. Ubiquitin-dependent virus particle budding without viral protein ubiquitination. PNAS 104(50):20031-6. Epub 2007 Dec 3.
  18. Bouamr, F., Houck-Loomis, B.R., De Los Santos, M., Casaday, R.J., Johnson, M.C., and Goff, S.P. 2007. The C-terminal portion of HRS interacts with TSG101 and interferes with HIV-1 Gag particle production. J Virology 81(6):2909-22. Epub 2006 Dec 20.
  19. Jouvenet N., Neil S.J.D., Bess, C., Johnson, M.C., Virgen, C.A., Simon, S.M., and Bieniasz, P.D. 2006. Plasma Membrane is the Site of Productive HIV-1 Particle Assembly. PLoS Biology 4(12):e435.
  20. Briggs,J.A.G., JohnsonM.C., Simon,M.N., Fuller,S.D., Vogt, V.M. 2004. Cryo-electron microscopy reveals conserved and divergent features of Gag packing in immature particles of Rous sarcoma virus and human immunodeficiency virus. J Molecular Biology 355(1):157-68. Epub 2005 Nov 2.
  21. Larson, D.R., Johnson, M.C. [co-author], Webb, W.W., and Vogt, V.M. 2005. Visualization of Retrovirus Budding with Correlated Light and Electron Microscopy. Proc Natl Acad Sci U S A. 102(43):15453-8. Epub 2005 Oct 17.
  22. Ako-Adjei D., Johnson, M.C., and Vogt, V. M. 2005. The retroviral CA domain dictates virion size, morphology and the co-assembly of Gag into virus-like particles Journal of Virology J Virology. 2005 Nov;79(21):13463-72.
  23. Johnson, M.C., Spidel J.L., Ako-Adjei D., Wills, J.W. and Vogt, V. M. (2005) The C-terminal half of TSG101 blocks Rous sarcoma virus budding and sequesters Gag into unique non-endosomal structures. J Virology 79:3775.
  24. Briggs, J. A. G., Simon, M., Gross, I., Kräusslich, H-G., Fuller, S. D., Vogt, V. M., and Johnson, M. C. [corresponding author] 2004. The stoichiometry of Gag protein in HIV-1. Nature Structural and Molecular Biology 11:672.
  25. Alonso M., Kim C. H., Johnson M. C., Pressley M., and Leong J. A. 2004. The NV Gene of Snakehead Rhabdovirus (SHRV) Is Not Required for Pathogenesis, and a Heterologous Glycoprotein Can Be Incorporated into the SHRV Envelope. J Virology 78:5875.
  26. Nandhagopal, N., Simpson, A. A., Johnson, M. C. , Francisco, A. B., Schatz , G. W., Rossmann, M. G., and Vogt, V. M. 2004. Dimeric Rous Sarcoma Virus Capsid Protein Structure Relevant to Immature Gag. J Molecular Biology 335:275.
  27. Altmann, S. M., Mellon, M. T., Johnson, M. C., Paw, B. H., Trede, N. S., Zon L.I., and Kim.C.H. 2004. Cloning And Characterization of an Mx Gene and its Corresponding Promoter from the Zebrafish, Danio rerio. Developmental and Comparative Immunology 28:295.
  28. Alonso, M., Johnson, M. C., Simon, B., and Leong, JA. 2003. A Fish Specific Expression Vector Containing the Interferon Regulatory Factor 1A (IRF1A) Promoter for Genetic Immunization of Fish. Vaccine 21:1591-600.
  29. Johnson, M. C., Scobie, H. M., Ma, Y. M. and Vogt, V. M. 2002. Nucleic acid-independent retrovirus assembly can be driven by dimerization. J Virology 76; 11177-85.
  30. Johnson, M. C., Scobie, H. M., and Vogt, V. M. 2001. The PR domain of Rous Sarcoma Virus (RSV) Gag Causes an Assembly/Budding Defect in Insect Cells. J Virology 75:4407-4412.
  31. Mangor, J. T., Monsma, S. A., Johnson, M. C., and Blissard, G.W. 2001. A GP64null Baculovirus Pseudotyped with the Vesicular Stomatitis Virus G Protein. J Virology 75:2544-2556.
  32. Kim C. H., Johnson, M. C., Drennan J. D., Simon, B. E., Thomann, E. and Leong J. C. 2000. DNA Vaccines Encoding Viral Glycoproteins Induce Non-specific Immunity and Mx Protein Synthesis in Fish. Journal of Virology 74:7048-7054.
  33. Leong, J. C., Crippen, T., Drennan, J., Johnson, M. C., Jordan, D., Kim, C., Simon, B., and Thomann, E. 2000. Development of DNA Vaccines for Fish. Suisanzoshoku 48:285-290.
  34. Johnson, M.C. and Leong, J.C. 2000. Generation of Recombinant Snakehead Rhabdovirus (SHRV); the NV Protein is not Required for Viral Replication. J Virology 74:2343-2350.

Lab Members