A “Spare Tire” for Proto-oncogene Promoters

A guanine tetrad (left) and G-quadruplex (right). Image courtesy of Wikimedia Commons.
A guanine tetrad (left) and G-quadruplex (right). Image courtesy of Wikimedia Commons.

Proto-oncogenes are genes that organisms rely on for normal growth and development but, when mutated or dysregulated, can cause cells to grow uncontrollably, resulting in cancer and metastasis. In some cases, a single DNA mutation is sufficient for cancer to develop. Why then, do so many proto-oncogene promoters contain strings of guanine residues, which are extremely vulnerable to DNA damage from factors such as oxidative stress and hyperinflammation, to control transcription levels? From an evolutionary viewpoint, this is a contradiction: DNA sequences that are the most vulnerable to damage and mutation are key to regulating one of the cell’s most dangerous classes of genes. This seems to be a recipe for genomic instability and disease. Fortunately, evolution has provided a very clever solution to this potential problem.

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