GATA-1 mediates auto-regulation of Gfi-1B transcription in K562 cells

Gfi-1B (growth factor independence-1B) gene is an erythroid-specific transcription factor, whose expression plays an essential role in erythropoiesis. Our laboratory has previously defined the human Gfi-1B promoter region and shown that GATA-1 mediates erythroid-specific Gfi-1B transcription. By further investigating the regulation of the Gfi-1B promoter, here we report that (i) Gfi-1B transcription is negatively regulated by its own gene product, (ii) GATA-1, instead of Gfi-1B, binds directly to the Gfi-1-like sites in the Gfi-1B promoter and (iii) Gfi-1B suppresses GATA-1-mediated stimulation of Gfi-1B promoter through their protein interaction. These results not only demonstrate that interaction of GATA-1 and Gfi-1B participates in a feedback regulatory pathway in controlling the expression of the Gfi-1B gene, but also provide the first evidence that Gfi-1B can exert its repression function by acting on GATA-1-mediated transcription without direct binding to the Gfi-1 site of the target genes. Based on these data, we propose that this negative auto-regulatory feedback loop is important in restricting the expression level of Gfi-1B, thus optimizing its function in erythroid cells.