Molecular cloning of FOG-2: A modulator of transcription factor GATA-4 in cardiomyocytes

GATA transcription factors are important regulators of both hematopoiesis ( GATA-1/2/3) and cardiogenesis (GATA-4) in mammals. The transcriptional acti vities of the GATA proteins are modulated by their interactions with other transcription factors and with transcriptional coactivators and repressors. Recently, two related zinc finger proteins, Ii-shaped (USH) and Friend of GATA-1 (FOG) have been reported to interact with the GATA proteins Pannier and GATA-1, respectively, and to modulate their transcriptional activities in vitro and in vivo. In this report, we describe the molecular cloning and characterization of a third FOG-related protein, FOG-2. FOG-2 is an 1,151 amino acid nuclear protein that contains eight zinc finger motifs that are structurally related to those of both FOG and USH. FOG-2 is first expressed in the mouse embryonic heart and septum transversum at embryonic day 8.5 a nd is subsequently expressed in the developing neuroepithelium and urogenit al ridge. In the adult, FOG-2 is expressed predominately in the heart, brai n, and testis. FOG-2 associates physically with the N-terminal zinc finger of GATA-4 both in vitro and in vivo. This interaction appears to modulate s pecifically the transcriptional activity of GATA-4 because overexpression o f FOG-2 in both NIH 3T3 cells and primary rat cardiomyocytes represses GATA -4-dependent transcription from multiple cardiac-restricted promoters. Take n together, these results implicate FOG-2 as a novel modulator of GATA-4 fu nction during cardiac development and suggest a paradigm in which tissue-sp ecific interactions between different FOG and GATA proteins regulate the di fferentiation of distinct mesodermal cell lineages.