Thioredoxin-Interacting Protein (TXNIP) Binding to GATA1 May Affect GATA1 Transcriptional Activity in Megakaryocytes

GATA1 is a crucial transcription factor for both megakaryopoiesis and erythropoiesis. In our previous work, we established a murine megakaryocyte-erythroid progenitor (MEP) cell line, named G1ME2 cells, which can be maintained with doxycycline (dox)-induced anti- Gata1 shRNA. These cells can differentiate into erythroid cells or megakaryocytes upon removal of dox; however, their megakaryocyte differentiation potential showed alterations after prolonged cell culture (90-100 days). Notably, CD41 expression in G1ME2 cells declined during long-term culture, prompting us to investigate the disparities between CD41+ and CD41- G1ME2 cells using total RNA sequencing. Interestingly, the western blotting analysis revealed a significant enrichment of thioredoxin-interacting protein (TXNIP) in the late G1ME2 cells compared to the early cells. TXNIP is known for its role in regulating cellular metabolism, and recently, we observed age-associated thrombocytopenia in TXNIP knockout mice, suggesting its involvement in hematopoiesis. Additionally, previous studies have identified its role in erythropoiesis through diverse mechanisms. In our current study, we made a novel discovery that TXNIP directly binds to GATA1 during megakaryopoiesis. Furthermore, deletion of GATA1 C-terminal enhanced binding affinity, implying that this interaction might occur when GATA1 is not localized to DNA. Consistently, TXNIP exhibited the ability to suppress GATA1 promoter activity, leading to changes in GATA1 localization in the presence or absence of TXNIP. In conclusion, our findings demonstrate the involvement of TXNIP in megakaryopoiesis, partially through the regulation of GATA1 transcriptional activity.