Topic summary
HRAS
GTPase HRas, also known as the "Harvey Rat sarcoma viral oncogene homolog" and transforming protein p21, is an enzyme that is encoded by the HRASgene in humans. The HRAS gene is located on the short (p) arm of chromosome 11 at position 15.5, from base pair 522,241 to base pair 525,549. HRas is a small G protein in the Ras subfamily of the Ras superfamily of small GTPases. Once bound to guanosine triphosphate, H-Ras will activate a Raf kinase like c-Raf, the next step in the MAPK/ERK pathway.
The gene was initially discovered in the Harvey rat sarcoma virus as a viral oncogene (Harvey murine sarcoma virus, Gammaretrovirus Hamursar), hence its name. The gene carried by this virus was later discovered to closely resemble a normal cellular gene found in many animals. From this, it was deduced that the virus had captured this cellular gene at some point in its evolutionary history. Once incorporated, the gene gave the virus the capability to disrupt normal cell growth, turning it into an oncovirus. Incorporation of cellular genes happens regularly in retroviruses; when a key regulatory gene such as HRAS is incorporated, it may become oncogenic as the virus continues to evolve. The benign version in the cellular genome is not directly cancerous, but further mutations can turn it cancerous. As a result, the cellular version is called a proto-oncogene.