The cellular regulators PTEN and BMI1 help mediate NEUROGENIN-3-induced cell cycle arrest.

Neurogenin-3 (NEUROG3) is a helix-loop-helix (HLH) transcription factor involved in the production of endocrine cells in the intestine and pancreas of humans and mice. However, the human NEUROG3 loss-of-function phenotype differs subtly from that in mice, but the reason for this difference remains poorly understood. Because expression precedes exit of the cell cycle and the expression of endocrine cell markers during differentiation, we investigated the effect of lentivirus-mediated overexpression of the human gene on the cell cycle of BON4 cells and various human nonendocrine cell lines. overexpression induced a reversible cell cycle exit, whereas expression of a neuronal lineage homolog, , had no such effect. In endocrine lineage cells, the cellular quiescence induced by short-term expression required cyclin-dependent kinase inhibitor 1A (CDKN1A)/p expression. Expression of endocrine differentiation markers required sustained expression in the quiescent, but not in the senescent, state. Inhibition of the phosphatase and tensin homolog (PTEN) pathway reversed quiescence by inducing cyclin-dependent kinase 2 (CDK2) and reducing p21 and NEUROG3 protein levels in BON4 cells and human enteroids. We discovered that expression stimulates expression of CDKN2a/p and (), with the latter limiting expression of the former, delaying the onset of CDKN2a/p -driven cellular senescence. Furthermore, NEUROG3 bound to the promoters of both and genes, and BMI1 attenuated NEUROG3 binding to the / promoter. Our findings reveal how human NEUROG3 integrates inputs from multiple signaling pathways and thereby mediates cell cycle exit at the onset of differentiation.