Serum amyloid A activating transcription factor-1 (SAF-1) plays a major role in regulating transcription of several inflammation responsive genes including SAA and MMP-1 that are implicated in the pathogenesis of reactive secondary amyloidosis, atherosclerosis and arthritis. SAF-1 is a 477-amino acid protein with six zinc fingers. Its activation during inflammatory condition by a phosphorylation event that leads to an altered structure, suggested possible structural modification of this protein as a leading cause of higher activity. However, no information is available regarding structural features which might regulate its activity. Here, we have characterized its functional domains, delineating activation and repression modules, DNA-binding and nuclear localization activities. Using GAL4AD-chimeras and DNA-binding assay with proteins prepared from various deletion constructs, the core DNA-binding domain of SAF-1 is mapped between amino acids 282 to 361 that contain second, third and fourth zinc fingers. Results from several deletion and point mutants using GFP reporter show that SAF-1 contains two independent nuclear localization signals; one is composed of a stretch of basic amino acids and the other is a bipartite signal located within the core DNA-binding domain. SAF-1 contains several negative and positively functioning transactivation modules clustered at the two ends of this protein. Removal of any one of the terminal negative modules renders the SAF-1 protein to be functionally very active. These findings suggest that the terminal repression modules act in conjunction to regulate the functional activity of this protein.