In mammals, the three classical ras genes encode four highly homologous proteins, N-Ras, H-Ras, and the isoforms K-Ras 4A and 4B. Previous studies have shown that K-ras is essential for mouse development and that while K-ras 4A and 4B are expressed during development, K-ras 4A expression is regulated temporally and spatially and occurs in adult kidney, intestine, stomach, and liver. In the pres...

Exclusive activation of either the Harvey-, Kirsten-, or N-ras gene is often found in human and rodent cancers, although the mechanisms responsible for tissue-specific ras gene activation are poorly understood. In this study, the contribution of ras gene expression and Ras protein activity to the tissue-specificity of ras gene activation was investigated using the rat mammary carcinogenesis mod...

Ras expression has been suggested as a marker for tumor aggressiveness of breast cancer,including the degrees of invasion and tumor recurrence.We showed previously that H-ras, but not N-ras, up-regulates matrix metalloproteinase 2 expression and induces invasive phenotype in MCF10A human breast epithelial cells (A. Moon, et al. Int. J. Cancer, 85: 176-181, 2000). In this study, we show that H-r...

STP-C488 (STP of herpesvirus saimiri [HVS] group C strain 488 [C488]) is the only virus-encoded protein found to associate with cellular ras and activate ras signal transduction pathways. To investigate an important role for ras signal transduction in STP-dependent growth transformation, we constructed recombinant strains of HVS C488 in which the STP-C488 oncogene was replaced with cellular nor...

We have studied whether hSOS1, a mammalian guanine nucleotide exchange factors responsible for activating Ras in response to growth factor stimulation, requires post-translational processing of Ras proteins to promote guanine nucleotide exchange. Our results showed that full-length hSOS1 catalyzed guanine nucleotide exchange on prenylated K-Ras(4B) but with a much lower efficiency on unprocesse...

rivers are important water resources for human life, but sometimes cause irreparable damages. the flood plains are fertile terrains which are endangered by flood. flood hazard mapping is one of the basic methods in flood fighting. in order to decline flood damages, the simulation of the hydraulic behavior of the rivers during flood occurrence is very important. in this study, areas that are flo...

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Constitutively active RAS small GTPases promote the genesis of human cancers. An important goal in cancer biology is to identify means of countervailing activated RAS signaling to reverse malignant transformation. Oncogenic K-RAS mutations are found in virtually all pancreatic adenocarcinomas, making the RAS pathway an ideal target for therapeutic intervention. How to best contravene hyperactiv...