In most mammals, prostaglandin F2 (PGF2) is believed to be a trigger that induces the regression of the corpus luteum (CL), whereby progesterone synthesis is inhibited, the luteal structure involutes, and the reproductive cycle resumes. Studies have shown that the early growth response 1 (EGR1) protein can induce the expression of pro-apoptotic proteins, suggesting that EGR1 may play a role in luteal regression. Our hypothesis is that EGR1 mediates the actions of PGF2 by inducing the expression of transforming growth factor beta 1 (TGFB1), a key tissue remodeling protein. The levels of EGR1 mRNA and protein were up-regulated in the bovine CL during PGF2-induced luteolysis in vivo and in PGF2-treated luteal cells in vitro. Using chemical and genetic approaches, the RAF/MEK1/ERK pathway was identified as a proximal signaling event required for the induction of EGR1 in PGF2-treated cells. Treatment with PGF2 increased the expression of TGFB1 mRNA and protein as well as the binding of EGR1 protein to TGFB1 promoter in bovine luteal cells. The effect of PGF2 on TGFB1 expression was mimicked by a PKC/RAF/MEK1/ERK activator or adenoviral-mediated expression of EGR1. The stimulatory effect of PGF2 on TGFB1 mRNA and TGFB1 protein secretion was inhibited by blockade of MEK1/ERK signaling and by adenoviral-mediated expression of NAB2, an EGR1 binding protein that inhibits EGR1 transcriptional activity. Treatment of luteal cells with TGFB1 reduced progesterone secretion, implicating TGFB1 in luteal regression. These studies demonstrate that PGF2 stimulates the expression of EGR1 and TGFB1 in the CL. We suggest that EGR1 plays a role in the expression of genes whose cognate proteins coordinate luteal regression.