V-maf Musculoaponeurotic Fibrosarcoma Oncogene F （MAFF） which is expressed in the term myometrium and kidney is a basic leucine zipper （bZIP） transcription factor which lacks a transactivation domain. MAFF is known to bind the US-2 DNA element in the promoter of the oxytocin receptor （OTR） gene and probably heterodimerizes along with other leucine zipper-containing proteins to enhance expression of the OTR gene throughout pregnancy period. MAFF also forms homodimers， and since it lacks a transactivation domain， the homodimer operates as a repressor of transcription.
