Department of Biochemistry
Iowa City, IA 52242-1109 USA
fax: (319) 335-9570
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M. Todd Washington, PhD
and Radiation Oncology
Carver College of Medicine
University of Iowa
51 Newton Rd, 4-734 BSB
Iowa City, IA 52242
Phone: (319) 335-7518
Lab Phone: (319) 335-7501
Fax: (319) 335-9570
The accumulation of somatic mutations in an estimated four to seven key genes is necessary for the development of most human cancers. These mutations lead to aberrant cell proliferation by activating proto-oncogenes and inactivating tumor suppressor genes. Consequently, factors increasing the cellular mutation rate accelerate the onset of cancers; those decreasing the mutation rate delay it. Thus, understanding how mutations arise is important to understanding carcinogenesis and to developing novel approaches to prevent it.
Our laboratory studies the mechanisms by which mutations occur in eukaryotic cells. It turns out that most mutations result from the replication of damaged DNA. DNA damage is problematic because it blocks replication by classical DNA polymerases – those involved in normal DNA replication and DNA repair. Without a means of overcoming these replication blocks, cells cannot divide. For this reason, cells possess several non-classical polymerases capable of replicating through DNA damage.These non-classical polymerasesare highly error-prone and are responsible for themisincorporation events that ultimately give rise to the mutations.
Our long-term goal is to understand the mechanisms of non-classical DNA polymerases and various replication accessory factors involved in mutagenesis. We use a variety of approaches including biochemical studies (ligand binding studies, enzyme activity assays), structural biology (X-ray crystallography, X-ray scattering), and cell-based techniques (yeast genetics, human tissue culture). We hope that this work will contribute to our understanding of the origins of mutations and cancers and perhaps gain new insights into their prevention.
Freudenthal, B.D., Brogie, J.E., Gakhar, L., Kondratick, C.M., and Washington, M.T. (2011) Crystal structure of SUMO-modified proliferating cell nuclear antigen. J. Mol. Biol. 406:9-17.
Dieckman, L.M., Johnson, R.E., Prakash, S., and Washington, M.T. (2010) Pre-steady state kinetic studies of the fidelity of nucleotide incorporation by yeast DNA polymerase delta. Biochemistry 49:7344-7350.
Freudenthal, B. D., Gakhar, L., Ramaswamy, S. and Washington, M. T. (2010) Structure of monoubiquitinated PCNA and implications for translesion synthesis and DNA polymerase exchange. Nat. Struct. Mol. Biol. 17:479-484.
Washington, M. T., Carlson, K. D., Freudenthal, B. D. and Pryor, J. M. (2010) Variations on a theme: eukaryotic Y-family DNA polymerases. Biochim. Biophys. Acta 1804:1113-1123.
Freudenthal, B. D., Gakhar, L., Ramaswamy, S. and Washington, M. T. (2009) A charged residue at the subunit interface of PCNA promotes trimer formation by destabilizing alternate subunit interactions. Acta Crystallogr. D 65:560-566.
Freudenthal, B. D., Ramaswamy, S., Hingorani, M. M. and Washington, M. T. (2008) Structure of a mutant form of proliferating cell nuclear antigen that blocks translesion DNA synthesis. Biochemistry 47:13354-13361.
Howell, C. A., Kondratick, C. M. and Washington, M. T. (2008) Substitution of a residue contacting the triphosphate moiety of the incoming nucleotide increases the fidelity of yeast DNA polymerase zeta. Nucleic Acids Res. 36:1731-1740.
Howell, C. A., Prakash, S. and Washington, M. T. (2007) Pre-steady-state kinetic studies of protein-template-directed nucleotide incorporation by the yeast Rev1 protein. Biochemistry 46:13451-13459.
Carlson, K.D., Johnson, R.E., Prakash, L., Prakash, S., and Washington, M.T. (2006) Human DNA polymerase kappa forms nonproductive complexes with matched primer termini but not with mismatched primer termini. Proc. Natl. Acad. Sci. USA. 103:15776-15781.
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