Gfi1b negatively regulates Rag expression directly and via the repression of FoxO1

Precise regulation of Rag (recombination-activating gene) expression is crucial to prevent genomic instability caused by the generation of Rag-mediated DNA breaks. Although mechanisms of Rag activation have been well characterized, the mechanism by which Rag expression is down-regulated in early B cell development has not been fully elucidated. Using a complementary DNA library screen, we identified the transcriptional repressor Gfi1b as...