Transcriptomal profiling of site-specific Ras signals.

Ras proteins are distributed in distinct plasma-membrane microdomains and endomembranes. The biochemical signals generated by Ras therein differ qualitatively and quantitatively, but the extent to which this spatial variability impacts on the genetic program switched-on by Ras is unknown. We have used microarray technology to identify the transcriptional targets of localization-specific Ras subsignals in NIH3T3 cells expressing H-RasV12 selectively tethered to distinct cellular microenvironments. We report that the transcriptomes resulting from site-specific Ras activation show a significant overlap. However, distinct genetic signatures can also be found for each of the Ras subsignals. Our analyses unveil 121 genes uniquely regulated by Ras signals emanating from plasma-membrane microdomains. Interestingly, not a single gene is specifically controlled by lipid raft-anchored Ras. Furthermore, only 9 genes are exclusive for Ras signals from endomembranes. Also, we have identified 31 genes common to the site-specific Ras subsignals capable of inducing cellular transformation. Among these are the genes coding for Vitamin D receptor and for p120-GAP and we have assessed their impact in Ras-induced transformation. Overall, this report reveals the complexity and variability of the different genetic programs orchestrated by Ras from its main sublocalizations.