Functional cooperation between GATA factors and cJUN on the star promoter in MA-10 Leydig cells.

Steroid hormone biosynthesis requires the steroidogenic acute regulatory protein (STAR). STAR is part of a protein complex that transports cholesterol through the mitochondrial membrane where steroidogenesis begins. Several transcription factors participate to direct the proper spatiotemporal and hormonal regulation of the Star gene in Leydig cells. Mechanistically, this is believed to involve the functional interplay between many of these factors. Here we report a novel transcriptional cooperation between GATA factors and cJUN on the mouse Star and human STAR promoters in MA-10 Leydig cells. This cooperation was observed with different GATA members (GATA1, 4, and 6), whereas only cJUN could cooperate with GATA factors. GATA/cJUN transcriptional cooperation on the Star promoter is mediated via closely juxtaposed GATA and AP-1 binding motifs. Mutation of all functional GATA and cJUN elements abolished GATA/cJUN cooperation, which is in agreement with previous data reporting a direct interaction between GATA4 and cJUN in a heterologous system. These data add valuable new insights that further define the molecular mechanisms that govern Star transcription in steroidogenic cells of the testis.