The aberrant expression of an oncogenic ETS transcription factor is implicated in the progression of the majority of prostate cancers, 40% of melanomas, and most cases of gastrointestinal stromal tumor and Ewing's sarcoma. Chromosomal rearrangements in prostate cancer result in overexpression of any one of four ETS transcription factors. How these four oncogenic ETS genes differ from the numerous other ETS genes expressed in normal prostate and contribute to tumor progression is not understood. We report that these oncogenic ETS proteins, but not other ETS factors, enhance prostate cell migration. Genome-wide binding analysis matched this specific biological function to occupancy of a unique set of genomic sites highlighted by the presence of ETS-and AP-1-binding sequences. ETS/AP-1-binding sequences are prototypical RAS-responsive elements, but oncogenic ETS proteins activated a RAS/MAPK transcriptional program in the absence of MAPK activation. Thus, overexpression of oncogenic ETS proteins can replace RAS/MAPK pathway activation in prostate cells. The genomic description of this ETS/AP-1-regulated, RAS-responsive, gene expression program provides a resource for understanding the role of these ETS factors in both an oncogenic setting and the developmental processes where these genes normally function.[Keywords: prostate cancer; ETS; ChIP-seq; RAS/MAPK; cell migration] Supplemental material is available for this article. In cancer cells, aberrant gene expression programs result from alterations in the signaling pathways that regulate transcription factor function, or from the mutation or altered expression of transcription factors themselves. Deciphering the role of a transcription factor requires understanding how these proteins are targeted to specific genomic binding sites, how they influence transcription once bound, and how these functions are modified by signaling pathways. However, overlapping functions among the thousands of transcription factors encoded by the human genome has made it difficult to assign specific oncogenic mechanisms.The ETS family of transcription factors exemplifies this specificity problem (Hollenhorst et al. 2011a). The 28 human ETS proteins bind DNA via a conserved ETS DNAbinding domain and recognize similar DNA sequences. All ETS proteins bind sites with the core sequence GGA and most bind with highest affinity to the extended consensus CCGGAAGT (Wei et al. 2010). This lack of intrinsic DNA sequence specificity is contrasted by unique biological functions for each ETS family member (Hollenhorst et al. 2011a). We showed previously that genomic targets of ETS transcription factors can include two distinct classes (Hollenhorst et al. 2007(Hollenhorst et al. , 2009. First are the ''redundant'' binding sites found in the proximal promoters of housekeeping genes. Binding sites in this class are characterized by the consensus ETS sequence (CCGGAAGT) and thus have the potential to bind any ETS protein with relatively high affinity. Second are the ''specific'' binding sites that are found...