STAT5a regulates the GlcNAc-1-phosphate transferase gene transcription and expression

The dolichyl-phosphate alpha-N-acetylglucosaminephosphotransferase 2 (Dpagt2) gene in the mouse has a housekeeping promoter, and its expression is regulated during the development and hormonally modulated lactogenesis of the mammary gland. Previous studies showed that the transcription of the mouse mammary Dpagt2 gene is stimulated by the lactogenic hormones, insulin, glucocorticoid receptor (GR), and prolactin. Transcription factors which bind to the Dpagt2 gene promoter region can influence the expression level of the Dpagt2 gene. It is supposed that the Dpagt2 gene promoter region (bases pairs -1462 to -5) maybe contain 10 putative STAT (signal transducer and activator of transcription) binding sites: TTN (5/6) AA. In order to identify the STAT factors involved in the transcription of the GPT gene, 32P labeling probes and lactating mouse nuclear extracts were prepared. Electrophoretic Mobility Shift Assays (EMSA) show that the region (bases pairs -386 to -322, where there is a STAT binding site, TTTCAAAAA) binds to STAT5a, not to glucocorticoid receptor (GR) or other STAT factors. The involvement of STAT5a in regulating the expression of the mouse Dpagt2 gene was further investigated by transient transfections of various Dpagt2 promoter/luciferase (Luc) constructs into COS 7 cells. The results showed that co-transfection of STAT5a or prolactin receptor can enhance Dpagt2 promoter activities in the promoter construct pGL-MX6 (from base pairs -386 to -5), but not in the promoter construct pGL-MX7 (from base pairs -322 to -5). This paper first reports that STAT5a is involved in the binding between -386 and -322 base pairs of the Dpagt2 gene promoter and stimulates the expression of the Dpagt2 gene transcription in the mouse lactating mammary gland.