THE ROLE OF TRANSCRIPTION ENHANCER FACTOR-I (TEF-1) RELATED PROTEINS IN THE FORMATION OF M-CAT BINDING COMPLEXES IN MUSCLE AND NONMUSCLE TISSUES

M-CAT sites are required for the activity of many promoters in cardiac and skeletal muscle. M-CAT binding activity is muscle-enriched, but i s found in many tissues and is immunologically related to the HeLa tra nscription enhancer factor-1 (TEF-1). TEF-1-related cDNAs (RTEF-1) hav e been cloned from chick heart. RTEF-1 mRNA is muscle-enriched, consis tent with a role for RTEF-1 in the regulation of muscle-specific gene expression. Here, we have examined the tissue distribution of TEF-1-re lated proteins and of M-CAT binding activity by Western analysis and m obility shift polyacrylamide gel electrophoresis. TEF-1-related protei ns of 57, 54 and 52 kDa were found in most tissues with the highest le vels in muscle tissues. All of these TEF-1-related proteins bound M-CA T DNA and the 57- and 54-kDa TEF-1-related polypeptides were phosphory lated. Proteolytic digestion mapping showed that the 54-kDa TEF-1-rela ted polypeptide is encoded by a different gene than the 52- and 57-kDa TEF-1-related polypeptides. A comparison of the migration and proteol ytic digestion of the 54-kDa TEF-1-related polypeptide with proteins e ncoded by the cloned RTEF-1 cDNAs showed that the 54-kDa TEF-1-related polypeptide is encoded by RTEF-1A. High resolution mobility shift pol yacrylamide gel electrophoresis showed multiple M-CAT binding activiti es in tissues. All of these activities contained TEF-1-related protein s. One protein-M-CAT DNA complex was muscle-enriched and was up-regula ted upon differentiation of a skeletal muscle cell line. This complex contained the 54-kDa TEF-1-related polypeptide, Therefore, RTEF1-A pro tein is a component of a muscle-enriched transcription complex that fo rms on M-CAT sites and may play a key role in the regulation of transc ription in muscle.