Acts as a transcriptional activator or repressor. Positively regulates the expression of alpha-A crystallin genes during lens fiber cell differentiation. Binds to Maf recognition elements (MARE). Homodimer or heterodimer with other bHLH-Zip transcription factors (By similarity). Binds DNA as a homodimer or heterodimer. Self-associates; the interaction requires the intact MAFB leucine-zipper domain. Interacts with FOS, HOXD12 and PRRX1. Expressed in brain, thymus, gut, lung, mesenterium, spleen, kidney, ovary and bursa. Expressed in the lens placode at stages 5, 8 and 14. Expressed at stage 18 when the invaginating lens placode closes to form the lens vesicle. Belongs to the bZIP family. Maf subfamily.