Stephen Kowalczykowski

image of Stephen Kowalczykowski

Distinguished Professor


Microbiology and Molecular Genetics

Offices and Labs

Briggs Hall 310
Briggs 303, 304, 306, 307
530-754-9704, 9703, 9702, 9705,
Life Science 3243


1976 PhD Chemistry (Biochemistry) Georgetown University
1972 BS Chemistry Rensselaer Polytechnic Institute

Research Contribution

Our research is focused on the molecular mechanisms of homologous recombination, with the long-term objective being the reconstitution of in vitro systems that accurately reproduce the cellular processes. Present research is centered on the biochemical mechanism and biological function of enzymes, protein-DNA interactions and DNA intermediates relevant to recombinational repair in bacteria, yeast, and humans. The experimental approaches include molecular genetic, biochemical, biophysical, and single-molecule techniques. The recent development of both high-resolution fluorescence microscopy and microfluidic methods enables visualization of individual proteins functioning on single molecules of DNA in real-time, permitting "visual" biochemistry.

Research Interests

Biochemical mechanisms of DNA recombination and single-molecule visualization of protein-DNA interactions

Biochemical mechanism of genetic recombination and DNA repair; DNA helicases and motor proteins; Physical and structural aspects of protein-nucleic acid interactions; Single-molecule biophysics; Nanotechnology; Cancer biology.


Phi Lambda Upsilon, Chemical Honor Society, 1971
Sigma Xi, 1974
American Cancer Society Postdoctoral Fellowship, 1977-1980
American Cancer Society Junior Faculty Research Award, 1983-1986
National Institutes of Health MERIT Award, 2000-2010
American Association for the Advancement of Science, Fellow, 2001
American Academy of Microbiology, Fellow, 2003
University of California, Davis, Academic Senate Faculty Research Lecture Award, 2005
American Academy of Arts & Sciences, Fellow, 2005
National Academy of Sciences, Member, 2007
University of California, Davis, College of Biological Sciences, Faculty Research Award, 2011
Michael J. Gait Award, Nucleic Acids Group of the Royal Society of Chemistry, 2012
Harvey Lecture, The Harvey Society, 2012

Department and Center Affiliations

Department of Microbiology and Molecular Genetics
Department of Molecular and Cellular Biology


American Society for Biochemistry and Molecular Biology, FASEB
American Chemical Society, Division of Biological Chemistry
American Society for Microbiology
American Association for the Advancement of Sciences
Biophysical Society

CBS Grad Group Affiliations

Biochemistry, Molecular, Cellular and Developmental Biology
Integrated Genetics and Genomics

Specialties / Focus

Integrated Genetics and Genomics
  • Chromosome Biology
  • Computational Biology
Biochemistry, Molecular, Cellular and Developmental Biology
  • DNA Repair
  • Chromosome Dynamics and Nuclear Function
  • Cancer Biology
  • Molecular Genetics
  • Biochemistry
  • Molecular Medicine
  • Molecular Microbiology

Graduate Groups not Housed in CBS



Briggs Hall 306 website
  • Naofumi Handa, Satona Ono, Theetha Pavankumar, Nev Gilhooly, Jack Exell
Briggs Hall 304 website
  • Nastaran Hadizadeh, Steven Gore, Galina Drofyak, Valentin Taryanik
Briggs Hall 303 website
  • Hsu-Yang Lee, Ichiro Amitani, Pham Minh Tuan, Na Li
Briggs Hall 307 website
  • Paul Pease, Taeho Kim, Katsumi Morimatsu, Artym Lada

Teaching Interests

Bacterial physiology and genetics. Molecular biology and biochemistry. Biophysics. Principles of protein-nucleic acid interactions. Advanced concepts in DNA metabolism. DNA repair and recombination.


MIC 276 Adv Concepts DNA Metab (Spring)
MIC 263 Principles of Protein-Nucleic Acid Interactions (Winter)


11/16/2015 5:54:43 PM
  • Kowalczykowski, S.C. (2015). An overview of the molecular mechanisms of recombinational DNA repair. Cold Spring Harb. Perspect. Biol., 7. 10.1101/cshperspect.a016410

  • Rad, B., Forget, A.L., Baskin, R.J., and Kowalczykowski, S.C. (2015). Single-molecule visualization of RecQ helicase reveals DNA melting, nucleation, and assembly are required for processive DNA unwinding. Proc. Natl. Acad. Sci. U. S. A.

  • Bell, J.C., Liu, B., and Kowalczykowski, S.C. (2015). Imaging and energetics of single SSB-ssDNA molecules reveal intramolecular condensation and insight into RecOR function. eLife, 4.

  • Wang, A.T., Kim, T., Wagner, J.E., Conti, B.A., Lach, F.P., Huang, A.L., Molina, H., Sanborn, E.M., Zierhut, H., Cornes, B.K., Abhyankar, A., Sougnez, C., Gabriel, S. B., Auerbach, A. D., Kowalczykowski, S. C., and Smogorzewska, A. (2105). A dominant mutation in human RAD51 reveals its function in DNA interstrand crosslink repair independent of homologous recombination. Mol. Cell, 59, 478-490

  • Morimatsu, K., and Kowalczykowski, S.C. (2014). RecQ helicase and RecJ nuclease provide complementary functions to resect DNA for homologous recombination. Proc. Natl. Acad. Sci. U.S.A. 111, E5133-5142

  • Liu, B., Baskin, R.J., and Kowalczykowski, S.C. (2013). DNA Unwinding heterogeneity by RecBCD results from static molecules able to equilibrate. Nature, 500, 482–485
  • Paeschke, K., Bochman, M.L., Garcia, P.D., Cejka, P., Friedman, K.L., Kowalczykowski, S.C., and Zakian, V.A. (2013). Pif1 family helicases suppress genome instability at G-quadruplex motifs. Nature, 497, 458-62
  • Forget, A.L., Dombrowski, C.C., Amitani, I., and Kowalczykowski, S.C. (2013). Exploring protein-DNA interactions in 3D using in situ construction, manipulation, and visualization of individual DNA-dumbbells with optical traps, microfluidics, and fluorescence microscopy. Nature Protoc., 8, 525-538
  • Bell, J.C., Plank, J.L., Dombrowski, C.C., and Kowalczykowski, S.C. (2012). Direct imaging of RecA nucleation and growth on single molecules of SSB-coated ssDNA. Nature, 491, 274-278.
  • Cejka, P., Plank, J.L., Dombrowski, C.C., and Kowalczykowski, S.C. (2012). Decatenation of DNA by the S. cerevisiae Sgs1–Top3–Rmi1 and RPA complex: A mechanism for disentangling chromosomes. Mol. Cell, 47, 886-896.
  • Forget, A.L. and Kowalczykowski, S.C. (2012). Single-molecule imaging of DNA pairing by RecA reveals a 3-dimensional homology search. Nature, 482, 423–427.
  • Nimonkar, A.V., Genschel, J., Kinoshita, E., Polaczek, P., Campbell, J.L., Wyman, C., Modrich, P., and Kowalczykowski, S.C. (2011). BLM-DNA2-RPA-MRN and EXO1-BLM-RPA-MRN constitute two DNA end resection machineries for human DNA-break repair. Genes & Dev., 25 350-362.
  • Cejka, P., Cannavo, E., Polaczek, P., Masuda-Sasa, T., Pokharel, S., Campbell, J.L., and Kowalczykowski, S.C. (2010). DNA end resection by Dna2-Sgs1-RPA and its stimulation by Top3-Rmi1 and Mre11-Rad50-Xrs2. Nature, 467, 112-116
  • Jensen, R.B., Carreira, A., and Kowalczykowski, S.C. (2010). Purified human BRCA2 stimulates RAD51-mediated recombination. Nature, 467, 678-683