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Why
carcinogens cause cancer?
DNA
(Deoxyribonucleic acid), is a chemical found primarily in the nucleus of cells.
DNA carries the instructions for making all the structures and materials the body
needs to function. DNA
is organized as two complementary strands, head-to-toe, with bonds between them
that can be "unzipped" like a zipper, separating the strands.
| DNA
Structure | The
sugar-phosphate backbones spiral around the outer surface of DNA. Between
these backbones are two different sized grooves, designated the major and minor
grooves. The major groove is approximately 50% wider than the minor. Major
grooves in a helix refer to the larger of the unequal grooves that are formed
as a result of the double-helical structure of DNA. Minor
grooves in a helix refer to the smaller of the unequal grooves that are formed
as a result of the double-helical structure of DNA. Try
this to see the two grooves!!
Click the right mouse button over the image
Render --> Schemes --> CPK
Proteins
that interact with DNA often make contact with the edges of the base pairs that
protrude into the major groove. | | |
Carcinogens
cause cancer by altering DNA in cells, interfering with normal biological processes.
Usually cells are able to detect this and attempt to repair the DNA; if they cannot,
they undergo cell death to prevent further damage. When the damage interferes
with cell death or encourages cell division, cancer occurs. Rapidly dividing cells,
such as in skin, the stomach lining, breast tissue, and reproductive organs, are
particularly sensitive to carcinogens due to harmful DNA being quickly copied.
| [PDB:
1dxa] |
Small carcinogen
molecules generally bind to the minor grooves of DNA. Try
this to view clearly the carcinogen in the minor groove. Click
right mouse button over image
Select -->All
Render --> Scheme-->
CPK
Select --> Hetero --> All
Color ---> Atoms --->Yellow -->
Yellow |
Tobacco
smoke has also been identified as a rich source of dozens of carcinogens, including
benzopyrene,DNA damaged
by Benzopyrene-diol-epoxide Benzopyrene is a chemical found in cigarette smoke.
Benzopyrene is converted to Benzopyrene-diol-epoxide in the body, which can randomly
insert itself into the grooves of DNA. Once
bound in the groove, DNA is not able to be replicated or transcribed effectively.
This may cause
mutations in daughter cells or unfavorable effects on gene expression. |
