M. Solanas et E. Escrich, HA-RAS IN NORMAL AND TUMORAL TISSUES - STRUCTURE, FUNCTION AND REGULATION, Journal of physiology and biochemistry, 52(3), 1996, pp. 173-192
The c-Ha-ras1 gene belongs to an eucaryotic ubiquitous gene family whi
ch codes important molecules involved in the transduction of mitogenic
signals and of cellular differentiation. The c-Ha-ras1 estructure, in
four coding exons and a non-coding 5'exon, is highly preserved throug
hout evolution. This gene, which generates a 1.4 Kb transcript, is exp
ressed in practically all the cell lineages with a tissue-specific pat
tern. The coded protein, of 189 amino acids and 21 kDa, is a small pr
otein that binds guanine nucleotides (GTP/GDP), is associated with the
plasma membrane and possesses low intrinsic GTPase activity. p21ras f
unctions as a molecular switch active when GTP is bound to it and inac
tive in the GDP-bound form. Its activity is very tightly controlled in
the cell by various positive and negative control mechanisms. The ras
gene family is the most frequently involved in the development of hum
an and animal tumors. Qualitative (point mutations) and quantitative (
over expression) mechanisms of oncogenic activation have been describe
d. The possible relation between determined human Ha-ras1 alleles and
the predisposition to cancer has been suggested as well.