Poly(ADP-ribose) polymerase binds with transcription enhancer factor 1 to MCAT1 elements to regulate muscle-specific transcription

Striated muscle-specific expression of the cardiac troponin T (cTNT) gene i s mediated through two MCAT elements that act via binding of transcription enhancer factor 1 (TEF-1) to the MCAT core motifs and binding of an auxilia ry protein to nucleotides flanking the 5' side of the core motif. Using DNA -protein and protein-protein binding experiments, we identified a 140-kDa p olypeptide that bound both the muscle-specific flanking sequences of the mo st distal MCAT1 element and TEF-1. Screening of an expression library with the MCAT1 element yielded a cDNA encoding a truncated form of poly(ADP-ribo se) polymerase (PARP). Endogenous PARP from embryonic tissue nuclear extrac ts migrated as a 140-kDa protein. Recombinant full-length PARP preferential ly bound the wild-type MCAT1 element and was shown to physically interact w ith TEF-1. In addition, endogenous TEF-1 could be coimmunoprecipitated with PARP from extracts of primary skeletal muscle cells. Recombinant PARP was able to ADP-ribosylate TEF-1 in vitro. Inhibition of the enzymatic activity of PARP repressed expression of an MCAT1-dependent reporter in transiently transfected primary muscle cells. Together, these data implicate PARP as t he auxiliary protein that binds with TEF-1 to the MCAT1 element to provide muscle-specific gene transcription.