Identification of β-cell-specific insulin gene transcription factor RIPE3b1 as mammalian MafA

摘要

Of the three critical enhancer elements that mediate β-cell-specific and glucose-responsive expression of the insulin gene, only the identity of the transcription factor binding to the RIPE3b element (RIPE3b1) has remained elusive. Using a biochemical purification approach, we have identified the RIPE3b1 factor as a mammalian homologue of avian MafA/L-Maf (mMafA). The avian MafA is a cell-type determination factor that expressed ectopically can trig- ger lens differentiation program, but no mammalian homologue of avian MafA has previously been identified. Here, we report cloning of the human mafA (hMafA) and demonstrate that it can specifi- cally bind the insulin enhancer element RIPE3b and activate insulin- gene expression.