期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1992
卷号：89
期号：19
页码：9010-9014
DOI：10.1073/pnas.89.19.9010
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：MyoD and c-Myc, members of the large "basic-helix-loop-helix" family of proteins, regulate diverse aspects of both normal and neoplastic growth and specific gene regulation. These two proteins differ at 9 of the 14 amino acids that comprise the basic domains necessary for DNA binding and transcriptional control. Individual amino acids in the MyoD basic domain were mutated to those found at the analogous positions in c-Myc. Four classes of mutants were obtained: (i) those with no effects on MyoD-site binding or activation of MyoD-responsive genes, (ii) those with no effect on MyoD-site binding but with a loss of activation potential, (iii) those with a loss of both DNA binding and activation potential, and (iv) one mutant (mut 9, Leu122----Arg) that left MyoD-site binding unaffected but imparted a new c-Myc-site binding capability. mut 9 competed with wild-type protein for the activation of MyoD-responsive reporter genes but could, like c-Myc, also suppress the adenovirus major-late promoter, which contains a c-Myc binding site. Our studies thus identify specific amino acid residues in the MyoD basic domain that are important for its activity as a DNA-binding transcriptional activator. Most significantly, our results with mut 9 indicate that Leu122 of MyoD is a critical determinant of specific DNA binding and that mutation at this residue can alter this specificity.
