Genetic and Molecular Analysis of Suppressors of Ras Mutations

摘要

RAS GENES ENCODE SMALL GTPase proteins, which when mutated, have been shown to result in breast cancer as well as cancers in a variety of other tissues. The study of Caenorhabditis elegans and other model systems has demonstrated that Ras is part of a conserved Ras/MAPK signaling pathway involved in many aspects of development and cell regulation. The C. elegans vulva is induced by an EGF like signal that activates the Ras/MAPK pathway. Constitutively active alleles of ras lead to hyperactivity of the signal transduction pathway and result in a multivulva (Muv) phenotype where numerous pseudovulvae are formed from vulval precursor cells (VPCs). By initiating suppressor screens of activated let-60 ras, many previously unknown components of this pathway have been identified. One gene, sur-9, has been defined by a semi-dominant allele isolated in a screen for temperature sensitive mutations that suppress the let-60(n1046) allele. While homozygous, sur-9(ku258) can suppress let-60(n1046) from 80% Muv to <1% Muv. sur-9(ku258)/ + also suppresses the let-60(n1046) phenotype to 10% Muv. Additional genetic analysis has suggested that sur-9 acts at a late step in the Ras/MAPK signaling pathway. Animals carrying the sur-9(ku258) mutation are also unhealthy, semi-sterile and show defects in other developmental processes. sur-9(ku258) has been mapped to LG III and fine mapping is currently being carried out. We hope to report the cloning and elucidation of sur-9's molecular identity which could contribute to our knowledge of a highly conserved and important biological pathway. Additionally, we have taken a molecular approach to understanding downstream targets of this important biological pathway.