报告题目：Reversible Covalent Reactions of Nucleic Acids
报告人：Steven Rokita, Director, Graduate Training Program at the Interface of Chemistry and Biology
2013-Present Director, Graduate Training Program at the Interface of Chemistry and Biology
2012-Present Professor, Johns Hopkins University
1998-2012 Professor of Chemistry and Biochemistry, University of MD, College Park, MD
1995-1998 Associate Professor, University of MD, College Park, MD
1986-1995 Assistant, then Associate Professor, Stony Brook University, Stony Brook, NY
1984-1985 NIH Postdoctoral Fellow, Rockefeller University
1983 PhD Massachusetts Institute of Technology
1979 BS University of California at Berkeley
The vast majority of drugs and reagents designed to interact covalently with nucleic acids react irreversibly and stoichiometrically. Once the resulting lesions are repaired, their biological impact is minimal. In contrast, a reversible reagent has the potential to support a continuum of reoccurring reactions despite lesion repair. The potential utility for such a strategy will be tested after optimizing quinone methide alkylation and regeneration. This electrophilic intermediate is sufficiently promiscuous to act under control of its attached ligand and may be designed for either alkylation or cross-linking of a chosen nucleic acid target. Subtle changes in the linker used for conjugation also have a significant impact on reaction efficiency. Results to date suggest that specificity can be built into the linker as well as the site-directing ligand.
The photochemical [2+2] cyclization of adjacent pyrimidines is also reversible, but this has rarely been appreciated in biology. Nevertheless, a competition between formation and reversion of the resulting cyclobutane pyrimidine dimer (CPD) defines its highly variable accumulation. The kinetics of CPD formation was previously considered as the sole variable, but now the dynamics of formation and reversion is shown to contribute to CPD accumulation by demonstrating a rapid response of CPD profiles to a change in DNA conformation. Thus, the in vivo levels of CPD generated in a number of laboratories is influenced by conformation as well as sequence. Ultimately, regions of high CPD accumulation may be used to probe changes in DNA structure in response to natural cellular processes.