Abstract

The RAS1 /MAPK pathway participates in a wide array of cellular processes including proliferation, differentiation and survival. Also, oncogene driven activation of MAPK signalling is frequently associated to the development and progression of cancer. The RAS1 -triggered RAF -MEK-MAPK cascade that forms the backbone of this pathway is supported by a series of scaffolding and regulatory molecules that help in modulating signal strength and duration. Much of our present knowledge on the makeup of this pathway has been assembled from successive genetic screening experiments conducted in the fly and worm.

In order to circumvent the limitations associated with traditional genetic screening techniques, we conducted a RNAi based functional screening analysis to get a global picture of the RAS1 /MAPK regulatory network. We then used a set of secondary epistasis assays to position these genes in relation to the core pathway components. Integration of these results with a protein interaction network analysis revealed distinct complexes acting at different steps in pathway function. We focus on a potential RAF regulatory complex and on a large set of mRNA processing components acting downstream of MEK . These findings add depth to the growing network of factors that feed into this pathway at different levels and, in particular, identify mRNA processing as an important factor in RAS1 /MAPK signal control.