Determining how MAFA and MAFB transcription factors activity is influenced by structural differences predicted by AlphaFold2.

MAFA and MAFB are related basic-leucine-zipper domain containing transcription factors which have important regulatory roles in a variety of cellular contexts, including pancreatic islet hormone producing α and β cells. These proteins have similar as well as distinct functional properties, and here we first used AlphaFold2, an artificial intelligence-based structural prediction program, to obtain insight into the three-dimensional organization of their non-DNA binding/dimerization sequences. This analysis was conducted on the wildtype (WT) proteins as well the pathogenic MAFA (MAFA ) and MAFB (MAFB ) mutants, with structural differences revealed between MAFA and MAFB in addition to MAFA and MAFA , but not MAFB and MAFB . Functional analysis disclosed that the inability to properly phosphorylate at S70 in MAFB , like S65 in MAFA , greatly increased protein stability and enabled MAFB to accelerate cellular senescence in cultured cells. Significant differences were also observed in the ability of MAFA, MAFA , MAFB, and MAFB to cooperatively stimulate enhancer-driven activity in the presence of other islet-enriched transcription factors. Experiments performed on protein chimeras disclosed that these properties were greatly influenced by structural differences found between the WT and mutant proteins. In general, these results revealed that AlphaFold2 predicts features essential to protein activity.