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Thomas Jefferson University - Erica S. Johnson, PhD
Erica S. Johnson, PhD

Biochemistry & Molecular Biology
Thomas Jefferson University
Jefferson Medical College
Department of Biochemistry & Molecular Biology
Associate Professor

Mailing Address
233 South 10th Street, BLSB 231
Philadelphia, Pennsylvania 19107
United States
Contact Information
Phone: (215) 503-4616
Fax: (215) 503-5393
Ph.D., MIT, Cambridge, MA (1992)
Expertise and Research Interests
Covalent modifications of proteins play critical roles in most cellular processes through their ability to cause rapid and reversible changes in the functions of pre-existing proteins, multi-protein complexes and subcellular structures. This type of mechanism for regulating protein function is especially important in signal transduction pathways, in transcriptional regulation, and in the cell cycle.

We are using the budding yeast Saccharomyces cerevisiae to study a modification that involves attachment of the small ubiquitin-related protein SUMO to other proteins. SUMO (also called Smt3 in yeast) is found in all eukaryotes, and it is becoming clear that SUMO conjugation plays an important role in cell cycle control and proliferation in both yeast and mammalian cells. However, very little is known about the the molecular mechanism of SUMO function. S. cerevisiae is a powerful system for studying conserved processes such as SUMO conjugation because it can be easily manipulated in genetic, biochemical and cell biological studies, and the lessons learned are likely to be applicable to more complex organisms.

We are interested in two major areas related to SUMO conjugation. The first is the identification and characterization of the enzymes required for attaching SUMO to other proteins. We have identified the enzymes that carry out all three steps of the SUMO conjugation reaction. The enzymes responsible for the third step, so-called E3s or SUMO ligases, are likely to be the critical factors in selecting substrates for SUMO attachment and for regulating this process. We are in the process of investigating how E3s bind their substrates and how the cell uses E3s to regulate SUMO conjugation.

Our second major interest is in determining the biological function of SUMO conjugation in yeast. We are attempting to find proteins that are modified by SUMO using a combination of approaches. One strategy is to purify proteins bearing SUMO, followed by identification of the proteins by mass spectrometry. The other is to isolate yeast mutants that interact functionally with the SUMO pathway. These mutants could lead to identification of new substrates as well as other proteins that participate in SUMO-mediated processes.

Laboratory Staff
Biochemistry; Sumo; Ubiquitin-Like Proteins; Yeast
  • Silver H.R., Nissley J.A., Reed S.H., Hou Y.M., Johnson E.S. A role for SUMO in nucleotide excision repair. DNA Repair (Amst). 10: 1243-1251, 2011.
  • Xiong L., Chen X.L., Silver H.R., Ahmed N.T., Johnson E.S. Deficient SUMO attachment to Flp recombinase leads to homologous recombination-dependent hyperamplification of the yeast 2 micron circle plasmid. Mol. Biol. Cell. 20: 1241-51, 2009.
  • Knipscheer P., Flotho A., Klug H., Olsen J.V., van Dijk W.J., Fish A., Johnson E.S., Mann M., Sixma T.K., Pichler A. Ubc9 sumoylation regulates SUMO target discrimination. Mol. Cell 31: 371-382, 2008.
  • Uzunova K., Gottsche K., Miteva M., Weisshaar S.R., Glanemann C., Schnellhardt M., Niessen M., Scheel H., Hofmann K., Johnson E.S., Praefcke G.J., Dohmen R.J. Ubiquitin-dependent proteolytic control of SUMO conjugates. J. Biol. Chem. 282: 34167-34175, 2007.
  • Chen X.L., Silver H.R., Xiong L., Belichenko I, Adegite C, and Johnson ES. Topoisomerase I-dependent viability loss in Saccharomyces cerevisiae mutants defective in both SUMO conjugation and DNA repair. Genetics 177: 17-30, 2007.
  • Huang R.Y., Kowalski D., Minderman H., Gandhi N., and Johnson E.S. Small ubiquitin-related modifier pathway is a major determinant of doxorubicin cytotoxicity in Saccharomyces cerevisiae. Cancer Res. 67: 765-772, 2007.
  • Reindle, A., Belichenko, I., Bylebyl, G.R., Chen, X.L., Gandhi, N. and Johnson, E. S. Multiple domains in Siz SUMO ligases contribute to substrate selectivity. J. Cell Sci. 119: 4749-4757, 2006.
  • Wohlschlegel, J.A., Johnson, E.S., Reed, S.I. and Yates, J.R. 3rd. Improved identification of SUMO attachment sites using C-terminal SUMO mutants and tailored protease digestion strategies. J Proteome Res. 5: 761-770, 2006.
  • Nathan, D., Ingvarsdottir, K., Sterner, D.E., Bylebyl, G.R., Dokmanovic, M., Dorsey, J.A., Whelan, K.A., Krsmanovic, M., Lane, W.S., Meluh, P.B., Johnson, E.S. and Berger, S.L. Histone sumoylation is a negative regulator in Saccharomyces cerevisiae and shows dynamic interplay with positive-acting histone modifications. Genes Dev. 20: 966-976, 2006.
  • Sterner, D.E., Nathan, D., Reindle, A., Johnson, E.S. and Berger, S.L. Sumoylation of the yeast Gcn5 protein. Biochemistry 45: 1035-1042, 2006.
  • Jacquiau H.R., van Waardenburg R.C., Reid R.J., Woo M.H., Guo H., Johnson E.S and Bjornsti M.A. Defects in SUMO conjugation and deconjugation alter cell sensitivity to DNA topoisomerase I-induced DNA damage. J. Biol. Chem. 280: 23566-23575, 2005.
  • Chen, X.L., Reindle, A. and Johnson, E.S. Misregulation of 2 micron circle copy number in a SUMO pathway mutant. Mol. Cell. Biol. 25:4311-4320, 2005.
  • Wohlschlegel, J.A., Johnson, E.S., Reed, S.I. and Yates, J.R. 3rd. Global analysis of protein sumoylation in Saccharomyces cerevisiae. J. Biol. Chem. 279:45662-45668, 2004.
  • Johnson ES. Protein modification by SUMO. Annu Rev Biochem. 73:355-82, 2004.
  • Bylebyl GR, Belichenko I, Johnson ES. The SUMO isopeptidase Ulp2 prevents accumulation of SUMO chains in yeast. J Biol Chem. 278(45):44113-20, 2003.
  • Johnson ES. Ubiquitin branches out. Nat Cell Biol.4(12):E295-8.4(12):E295-8, 2002.
  • Johnson ES, Gupta AA. An E3-like factor that promotes SUMO conjugation to the yeast septins. Cell. 106(6): 735-44, 2001
  • Schwienhorst I, Johnson ES, Dohmen RJ. SUMO conjugation and deconjugation. Molecular and General Genetics. 263(5): 771-86, Jun 2000
  • Johnson ES, Blobel G. Cell cycle-regulated attachment of the ubiquitin-related protein SUMO to the yeast septins. Journal of Cell Biology. 147(5): 981-94, 1999
  • Ramos PC, Hockendorff J, Johnson ES, Varshavsky A, Dohmen RJ. Ump1p is required for proper maturation of the 20S proteasome and becomes its substrate upon completion of the assembly. Cell. 92(4): 489-99, 1998
  • Johnson ES, Schwienhorst I, Dohmen RJ, Blobel G. The ubiquitin-like protein Smt3p is activated for conjugation to other proteins by an Aos1p/Uba2p heterodimer. Embo Journal. 16(18): 5509-19, 1997
  • Johnson ES, Blobel G. Ubc9p is the conjugating enzyme for the ubiquitin-like protein Smt3p. Journal of Biological Chemistry. 272(43): 26799-802, 1997
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