The findings appear as the cover story in the latest issue of the Journal of Molecular Biology. This team was headed by Dinshaw Patel at MSKCC, Nicholas Geacintov, chair of NYU's chemistry department, and Suse Broyde, a professor in NYU's biology department.
The studied gene, p53, is an important tumor suppressor gene that plays critical roles in cellular functions such as cell-cycle control, differentiation, and DNA repair. Many different chemical carcinogens, including those that are primary components of cigarette smoke, are known to damage DNA. This damage occurs at special positions of the p53 gene, called mutation hot spots, which have been previously linked with cigarette smoke. This molecular link between chemical DNA damage and cigarette-associated lung cancer has been called the "smoking gun."
In the study, the conformational switch discovered by the research team entails a change in the conformation of a carcinogen-damaged site in a DNA model sequence similar to that in a p53 mutation hot spot. The change is brought about by the presence of a single methyl group (composed only of one carbon and three hydrogen atoms) on a cytosine base adjacent to the damaged site. Without this methyl group, the bulky chemical carcinogen resides at an external binding site in the minor groove of the DNA double helix. However, in the presence of this single methyl group, it assumes an intercalated structure in which the carcinogenic residue is sandwiched between adjacent base pairs in the double helix.
Source:New York University