The POU-homeodomain transcription factor Pit-1 governs ontogeny and cell-specific gene expression of pituitary lactotropes, somatotropes and thyrotropes. The splice isoform, Pit-1, inserts a 26-amino acid (AA) repressor at AA48 in the Pit-1 transcription activation domain (TAD). The Pit-1 TAD contains a basal regulatory subregion, R1 (AA1-45) and a basal and Ras responsive region, R2 (AA46-80). To precisely map these activities, we generated GAL4-Pit-1/Pit-1TAD fusions and, in full-length HA-Pit-1, a series of substitution mutants of R2. Analysis in GH4 cells identified an activation domain at AA50-70, followed by an overlapping, dual-function, Ras-responsive-inhibitory domain, located from AA60-80. In contrast, GAL4-Pit-1TAD repressed both basal and Ras-mediated TAD activity. To determine the functional interplay between TAD subregions and the -domain, we inserted the -domain every 10-AA across the 80-AA Pit-1 TAD. Like wildtype Pit-1, each construct retained transcriptional activity in HeLa cells and repressed the Ras response in GH4 cells. However, -domain insertion at AA61 and AA71 resulted in greater repression of Ras responsiveness, defining a critical R2 TAD spanning AA61-71 of Pit-1. Furthermore, Ras activation is augmented by Steroid receptor coactivator 1, whereas CBP is not a Ras mediator in this system. In summary, the Pit-1/Pit-1 TADs are comprised of multiple, modular and transferable subdomains, including a regulatory R1 domain, a basal activation region, a selective inhibitory-Ras responsive segment and a -specific repressor domain. These data provide novel insights into the mechanisms by which the Pit-1 TAD integrates DNA binding, protein partner interactions, and distinct signaling pathways to fine-tune Pit-1 activity.