LAUSR

Ets‐related transcription factor GA‐binding protein alpha (GABPα), which is encoded by Gabpa, is expressed in a variety of cell types and is involved in cellular functions such as cell cycle regulation, apoptosis, and differentiation. Here, we generated Gabpa conditional knockout embryonic stem cells (ESCs) and characterized its cellular phenotypes. Disruption of Gabpa revealed that the proliferation of Gabpa‐null ESCs was drastically repressed and cells started to die within 2 days. The repressed proliferation of Gabpa‐null ESCs was recovered by artificially forced expression of GABPα. Expression analysis showed that p53 mRNA levels were comparable; however, p53 target genes, including Cdkn1a/p21, Mdm2, and Gadd45a, were upregulated and cell cycle‐related genes, including Cyclin D1/D2 and Cyclin E1/E2, were downregulated in Gabpa‐null ESCs. Interestingly, p53 and cleaved Caspase3 expressions were enhanced in the cells and reduced proliferation as well as cell death of Gabpa‐null ESCs were rescued by either transfection of p53 RNAi or treatment of the p53 inhibitor pifithrin‐α. These results suggest that GABPα inhibits the accumulation of p53 and is involved in the proliferation and survival of ESCs. Stem Cells 2017;35:2229–2238