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“Influence of Nucleobase Modifications on DNA Repair and Processing by a Translesion Polymerase” featuring Christopher Wilds, Concordia University
December 15, 2017 @ 3:00 pm - 4:00 pm
Department Seminar Series:
“Influence of Nucleobase Modifications on DNA Repair and Processing by a Translesion Polymerase”
Department of Chemistry and Biochemistry
Friday, December 15, 2017
3:00 PM – 4:00 PM
McGaugh Hall 1246
DNA alkylation results from a variety of endogenous and/or exogenous agents that can interfere with processes such as replication and transcription. Alkyl appendages on the DNA scaffold can have adverse consequences such as DNA polymerase (Pol) blockage, nucleotide misincorporation and chromosomal instability. Fortunately, organisms have various repair pathways to restore damaged DNA. O6-alkylguanine DNA alkyltransferases (AGT) are responsible for the removal of mutagenic O6-alkyl 2’-deoxyguanosine and O4-alkyl thymidine adducts. AGT homologues show vast substrate differences with respect to the size of the adduct and which alkylated atoms they can restore. Our group has been interested in exploring AGTs ability to act upon inter- and intrastrand crosslinks in DNA. Oligonucleotide probes containing alkylene linkers varying in length that tether the O6 atom of 2’-deoxyguanosine or O4 atom of thymidine have been prepared using a combination of solution and solid phase synthesis. Our studies involving AGTs and the modified DNA probes have revealed that human AGT is capable of acting upon O6-alkylene-2’-deoxyguanosine crosslinks.
In the event that a lesion evades the process of DNA repair, translesion synthesis (TLS) by Y-family DNA Polymerases (Pols) can occur allowing bypass of the DNA lesion in an error-free or error-prone manner. For example, DNA Pol η in humans (hPol η) plays a pivotal role in the bypass of certain UV-induced DNA damage, which impedes DNA replication. Using thymidine analogs that link the C5 and O4 atoms by a dimethylene or trimethylene group, which limits the O4-lesion to adopt an anti-conformation, we investigated the influence of lesion orientation on hPol η processivity. These modifications were found hinder nucleotide incorporation by hPol η and single nucleotide incorporation studies revealed differences in selectivity in nucleotide incorporation for the conformationally restricted lesions relative to O4-methyl and O4-ethyl thymidine.
About Professor Christopher Wilds
Christopher Wilds received his BSc in Analytical Chemistry from Concordia University (Montréal, Canada) back in 1995. He obtained his PhD at McGill University (also in Montréal) in 1999 under the guidance of Masad Damha where he synthesized and investigated modified oligonucleotides containing 2-fluoro-2-deoxy-D-arabinose (2’F-ANA). The recipient of a NSERC postdoctoral fellowship, he acquired expertise in nucleic acid crystallography working with Martin Egli at Northwestern and Vanderbilt Universities. He then joined the lab of Paul Miller at Johns Hopkins University to investigate DNA repair. In 2003 Chris started his independent career at the Department of Chemistry and Biochemistry at Concordia as an Assistant Professor. The following year he became the Department’s first ever Canada Research Chair (Tier 2, Biological Chemistry). His laboratory has interests in the synthesis of chemically modified nucleic acids, with expertise in preparing site-specific lesions in DNA for repair assays to provide insights into the processing of poorly repaired and persistent forms of DNA damage. His research has been supported by numerous funding agencies and he is the author of over 65 publications.