Gonadotropin-releasing hormone activation of c-jun, but not early growth response factor-1, stimulates transcription of a luteinizing hormone beta-subunit gene.

Transcription of mammalian LH beta-subunit genes (LHbeta) is regulated by GnRH through activation of early growth response factor-1 (Egr-1), which interacts synergistically with steroidogenic factor-1 (Sf-1) and pituitary homeobox-1 (Pitx1) at the promoter; Egr-1 is thought to comprise the major mediator of this effect. However, the proximal promoters of LHbeta genes in lower vertebrates lack an Egr-1 response element yet are responsive to GnRH; we demonstrate here that the promoter of the Chinook salmon LHbeta (csLHbeta) gene is also unresponsive to Egr-1. The homologous LHbeta promoters in other fish contain a conserved estrogen response element-like sequence, which we recently demonstrated is not required for estrogen receptor (ER) alpha association with the csLHbeta gene.