Research Projects in the Geacintov Lab

Nicholas E. Geacintov

 

Overview.

The overall objective is to understand mechanisms and consequences of damage in genomic DNA induced by environmental contaminants and other reactive chemical species present in the human body, employing well defined model systems.

 

Background

The human genome is under continuing attack by chemicals in our environment, e.g.,  by reactive oxygen species and other chemicals that arise naturally due to a  variety of metabolic processes.   These exogenous and endogenous chemicals react with DNA to form chemical addition products (adducts), thus modifying the normal properties  of the DNA bases.   If not removed by various DNA repair mechanisms, these adducts will interfere with the transcription and replication of DNA and can cause the mutagenic insertion of the incorrect bases in the RNA transcripts and newly synthesized DNA molecules.  An accumulation of such mutations can lead to cancer.  Understanding the detailed mechanisms of these phenomena may led to novel strategies for preventing this and other genetic diseases that are caused by the chemical alterations of normal DNA.  

Polycyclic Aromatic DNA Adducts: Synthesis, Characterization, and biochemical function (DNA replication, transcrtiption, and DNA repair).   

The laboratory of Professor Geacintov focuses on studies of DNA model systems that include well defined oligonucleotides with single, chemically characterized, modified nucleic acid bases,  called DNA lesions.  One focus is on  polycyclic aromatic hydrocarbon (PAH) compounds that are derived from the combustion of fossil fuels and tobacco smoke, and contaminate our air, water, and food supplies.   The PAH are metabolized in living cells to diol epoxides that bind predominantly to guanine and adenine in DNA. One of the most fascinating properties of these PAH metabolites is that subtle structural or stereochemical differences between related isomeric molecules can give rise to dramatic differences in tumorigenesis that are rooted in the molecular structure-biological activity relationships. This molecular/biological puzzle is being investigated by a combination of synthetic, biochemical, physical, and computational modeling techniques in collaboration with other research groups at NYU and other institutions. The methods include high resolution gel electrophoresis to study structural distortions in DNA (bends, joints of flexibility), modern NMR methods (in collaboration with Dinshaw Patel at Memorial Sloan-Kettering Cancer Center in New York) to determine the three-dimensional structures of adducts, sensitive optical spectroscopic techniques to distinguish subtle physical characteristics of the adducts, enzyme kinetic studies of DNA repair and DNA replication in vitro and in cells (the latter in collaboration with others), and computer modeling techniques to better understand and visualize molecular structures and DNA-protein interactions (in collaboration with Suse Broyde, Biology Department).  

 

Laser Photophysics, Kinetic Transient Absorption Spectroscopy, and Gel Electrtophoresis Studies: Electron Transfer Reactions in DNA and Photochemistry at a Distance.

 

 Modern and sensitive laser flash photolysis techniques are employed to study the propagation of radicals in DNA formed by a variety of oxidative processes.  These experiments are conducted using some uniquely sensitive equipment in our laser laboratory.   Of special interest are mechanisms of proton-coupled electron transfer reaction mechanisms and DNA cleavage in PAH-DNA complexes and oligonucleotides containing well defined oxidized  DNA bases or nucleic acid analogs (2-aminopurine). 

 

 

    Professor Geacintov received his Ph.D. in 1961 from Syracuse University. Following postdoctoral training at  Brooklyn Polytechnic Institute, he joined the physics department's Radiation and Solid State Laboratory at New  York University in 1963. He has been a full-time faculty member of the chemistry department since 1969, and Chair since 1999. 

 

Some Recent Publications

 

Suri, A.K.; Mao, B.,  Amin, S.,  Geacintov, N.E.,  Patel, D. J.,  Solution Conformation of the (+)- trans-anti -benzo[g]chrysene-dA Adduct Opposite dT in a DNA Duplex .  J. Mol. Biol.  292(2),  289-307 (1999).

 

Tan, J.,  Geacintov, N.E.,  and  Broyde, S.,  Principles Governing Conformations in Stereoisomeric  Adducts of Bay Region Benzo[a]pyrene Diol Epoxides to Adenine in DNA: Steric and Hydrophobic Effects  Are Dominant, J. Am. Chem. Soc., 122,  3021‑3032 (2000).

 

Buterin, T., Hess, M.T., Luneva, N., Geacintov, N.E., Amin, S., Kroth, H., Seidel, A., and Naegeli, H., Lack of enzymatic repair of fjord polycyclic aromatic hydrocarbon-DNA adducts in ras codon 61 mutational hotspots. Cancer Res. 60, 1849-1856 (2000).

 

Rechkoblit, O., Amin, S., and Geacintov, N.E.,  Primer Length - Dependence of Formation of Monomeric and Dimeric DNA Polymerase I (Klenow Fragment) - Template/Primer Complexes Containing Site-Specific Bulky Lesions.. Biochemistry 38, 11834-11840 (1999).

 

Khan, A.U., Kovacic, D., Kolbanovskii, A.,  Desai, M., Frenkel, K., Geacintov, N.E.,   The Decomposition of  Peroxynitrite to Nitroxyl Anion (NO^-) and Singlet Oxygen in Aqueous Solution.  Proceed. Natl. Acad. Sci. USA 97, 2984-2989, 2000.

 

Shafirovich, V., Dourandin, A., Luneva, N. P., Geacintov, N. E. The Kinetic Deuterium Isotope Effect as a   Probe of a Proton Coupled Electron Transfer Mechanism in the Oxidation of Guanine by 2-Aminopurine  Radicals, The Journal of Physical Chemistry B104, 137-139 (2000).