M-CAT binding factor is related to the SV40 enhancer binding factor, TEF-1.

M-CAT binding factor (MCBF) governs the activity of the cardiac troponin T gene promoter. M-CAT motifs have also been implicated recently in the regulation of other contractile protein genes which like cardiac troponin T, do not require direct interaction with MyoD1 or related factors for activity. Mutational analysis of the M-CAT motif revealed that it can be functionally replaced by a regulatory motif of the SV40 enhancer which binds human transcription factor TEF-1. Biochemical analyses show that MCBF from muscle nuclei is indistinguishable from TEF-1 in terms of specificity of binding site recognition, fractionation on DNA-agarose, and apparent molecular weight. In addition, antibodies raised against amino- and carboxyl-terminal regions of human TEF-1 also bind to MCBF from chicken muscle. We conclude, therefore, that MCBF is closely related to TEF-1. Finally, MCBF/TEF-1 is highly enriched in the nuclei of striated muscle, as compared with other tissues, consistent with a role in muscle-specific promoter regulation.