Growth hormone is involved in GATA1 gene expression via STAT5B in human erythroleukemia and monocytic cell lines.

GATAs are a family of transcription factors consisting of six members. Particularly, GATA1 and GATA2 have been reported to promote the development of erythrocytes, megakaryocytes, eosinophils, and mast cells. However, little information is available on the extracellular ligands that promote GATA1 expression. We evaluated whether growth hormone (GH) is an extracellular stimulator that participates in the signal transduction of GATAs, focusing on GATA1 expression in hematopoietic cell lineages. We used a reporter assay, RT-PCR, real-time quantitative PCR, and western blotting to evaluate GH-induced expression of GATA1 and GATA2 in the human erythroleukemic cell line K562 and the non-erythroid cell line U937. GATA1 expression in these hematopoietic cell lines increased at the transcriptional and protein levels in the presence of GH, and was inhibited by a STAT5 specific inhibitor. Cells transfected with activated STAT5B showed increased expression of GATA1. We identified functional STAT5B consensus sequences as binding site-158 bp from the transcription starting site in the GATA1 promoter region. These results suggest that GH directly induces GATA1 expression via GHR/JAK/STAT5 and is related to hematopoietic cell proliferation.

Growth hormone directly stimulates GATA2 expression.

OBJECTIVE: GATA2 is a key transcription factor involved in the differentiation and determination of thyrotrophs and gonadotrophs in pituitary and hematopoietic development. However, studies on the upstream ligands of the GATA2 signal transduction pathway have been limited. To identify upstream ligands, we examined growth hormone (GH) as a plausible stimulator. DESIGN: We evaluated GH-induced GATA2 expression in murine TtT/GF thyrotrophic pituitary tumor cells and its direct impact on the GHR/JAK/STAT5 pathway using a combination of a reporter assay, real-time quantitative polymerase chain reaction, and western blotting. RESULTS: GATA2 expression increased with activated STAT5B in a dose-dependent manner and was inhibited by a STAT5 specific inhibitor. Moreover, we found functional STAT5B binding site consensus sequences at -359 bp in the GATA2 promoter region. CONCLUSION: These findings suggest that GH directly stimulates GATA2 via the GHR/JAK/STAT pathway and participates in various developmental phenomena mediated by GATA2.