We have recently demonstrated that a testicular GATA-binding protein, GATA-1, up-regulates the transcription of inhibin �-subunit gene through interaction with GATA motifs in the promoter region in MA-10, a mouse Leydig tumor cell line. In this study, we showed that both GATA-1 and GATA-4 also transactivated the transcription from the promoter for the 4.8-kb inhibin/activin �-B-subunit gene transcripts, �-B(4.8)-subunit promoter, in two testicular cell lines, MA-10 and MSC-1, which is a mouse Sertoli cell line. The abilities of GATA-1 and GATA-4 interacting with GATA and/or GATA-like sequences to transactivate the �-B(4.8)-subunit promoter were next examined by mutation analysis. Mutations of GATA or GATA-like sequences caused no apparent effect or only a small decrease in the basal transcriptional activity of this promoter. However, mutation of the GATA motif at �65 markedly decreased 60–70 % of the effect of GATA-1 on the transactivation of �-B(4.8)-subunit promoter in both MA-10 and MSC-1 cells. In addition, mutation of the GATA motif in MSC-1 cells also reduced 40–50 % of the effect of GATA-4 to transactivate this promoter. Interestingly, mutation of GATT at �42 caused a 70–90 % increase in the transactivation of �-B(4.8)-subunit promoter by GATA-1 or GATA-4. No significant change in the promoter activity was observed when GATT at �177 or GATC at �201 was mutated. Electrophoretic mobility shift assay confirmed the above observations that these GATA-binding proteins interacted with the GATA motif at �65 and GATT at �42, but not with GATC at �201 or GATT at �177. Serial deletion from the 5�-end of the basal promoter, from �226 to �90, markedly decreased the basal transcription, but increased the effect of GATA-1 on transactivation of the �-B(4.8)-subunit promoter. In summary, our observations suggest that the two GATA-binding proteins transactivate the �-B(4.8)-subunit promoter in testicular cells vi
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