García-España Antonio, Philips Mark R
Bionos Biotech SL; Biopolo Hospital La Fe, Valencia, Spain.
Perlmutter Cancer Center, New York University Grossman School of Medicine, New York, NY, USA.
Res Sq. 2023 Jan 20:rs.3.rs-2485219. doi: 10.21203/rs.3.rs-2485219/v1.
KRAS, HRAS and NRAS oncogenes belong to a family of 40 highly homologous genes, which in turn are a subset of a superfamily of >160 genes encoding small GTPases. RAS oncoproteins consist of a globular G-domain (aa1-166) and a 22-23aa unstructured hypervariable region (HVR) that mediates membrane targeting. The evolutionarily origins of the RAS isoforms, their HVRs and alternative splicing of the KRAS locus has not been explored. We found that KRAS is basal to the oncogene family and its duplication generated HRAS in the common ancestor of vertebrates. In a second round of duplication HRAS generated NRAS and KRAS generated an additional RAS gene we have designated KRASBL, absent in mammals and birds. KRAS4A arose through a duplication and insertion of the 4th exon of NRAS into the 3rd intron of KRAS. We found evolutionarily conservation of a short polybasic region (PBR1) in HRAS, NRAS and KRAS4A, a second polybasic region (PBR2) in KRAS4A, two neutralized basic residues (NB) and a serine in KRAS4B and KRASBL, and a modification of the CaaX motif in vertebrates with farnesyl rather than geranylgeranyl polyisoprene lipids, suggesting that a less hydrophobic membrane anchor is critical to RAS oncoprotein function. The persistence of four RAS isoforms through >400 MY of evolution argues strongly for differential function.
KRAS、HRAS和NRAS致癌基因属于一个由40个高度同源基因组成的家族，而这40个基因又是一个超家族的子集，该超家族包含超过160个编码小GTP酶的基因。RAS癌蛋白由一个球状G结构域（第1至166位氨基酸）和一个22 - 23个氨基酸的无结构高变区（HVR）组成，该高变区介导膜靶向作用。RAS亚型的进化起源、它们的HVR以及KRAS基因座的可变剪接尚未得到探索。我们发现KRAS是致癌基因家族的基础，其复制在脊椎动物的共同祖先中产生了HRAS。在第二轮复制中，HRAS产生了NRAS，KRAS产生了一个我们命名为KRASBL的额外RAS基因，该基因在哺乳动物和鸟类中不存在。KRAS4A是通过将NRAS的第4外显子复制并插入到KRAS的第3内含子中产生的。我们发现HRAS、NRAS和KRAS4A中一个短的多碱性区域（PBR1）在进化上具有保守性，KRAS4A中有第二个多碱性区域（PBR2），KRAS4B和KRASBL中有两个中和的碱性残基（NB）和一个丝氨酸，并且在脊椎动物中CaaX基序被法尼基化而非香叶基香叶基化的聚异戊二烯脂质修饰，这表明疏水性较低的膜锚定对于RAS癌蛋白功能至关重要。四种RAS亚型在超过4亿年的进化过程中持续存在，这有力地证明了它们具有不同的功能。
