Mechanism of tissue-specific transcription: interplay between positive and negative regulatory factors.
At least four regulatory cis-acting DNA sequences, CCAAAAGTGG (element A), TTATTTTTA (element B), TATTTATT (element C), and TATTACCTTTAT (element S), were identified in cardiac myosin light chain-2 (MLC2) proximal promoter as target sites for sequence-specific binding of nuclear proteins. For muscle-specific transcription, the proximal promoter (-53 to +1) consisting only of elements B and C is required. Addition of element A to this promoter results in a muscle-specific up-regulation, whereas the addition of element S exerts a negative effect on transcription. The negative and positive regulatory effects of elements S and A respectively were demonstrated by site-specific mutations of the promoter following transient transfection of cardiac muscle cells in culture. Elements S and A interact separately with distinct nuclear protein factor present in both muscle and non-muscle cells, even though their regulatory activities are restricted to muscle cells. Among the multiple complexes resulting from the interaction of nuclear proteins and elements S and A DNAs, one requires both S and A sequences together for binding. Element B, which exerts a muscle-specific positive effect on transcription, binds to a nuclear protein present in cardiac muscle, but not in non-muscle cells. DNA-protein binding assays and mutational analysis of the MLC2 promoter suggest that the contribution of the functionally opposed cis-elements depends upon an interplay between the positively and negatively acting DNA-binding proteins via protein-protein interactions to mediate opposite regulatory effects on gene transcription.
Zhou
M D
MD
Department of Anatomy and Cell Biology, State University of New York Health Science Center, Brooklyn 11203.
Wu
Y
Y
Kumar
A
A
Siddiqui
M A
MA
D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D002642:Chick Embryo; D004268:DNA-Binding Proteins / Q000502:physiology*; D003850:Deoxyribonuclease I; D005786:Gene Expression Regulation / Q000502:physiology; D005796:Genes / Q000235:genetics; D008969:Molecular Sequence Data; D009154:Mutation; D009687:Nuclear Proteins / Q000502:physiology*; D009928:Organ Specificity / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000502:physiology*; D012045:Regulatory Sequences, Nucleic Acid / Q000502:physiology*; D014158:Transcription, Genetic / Q000502:physiology*
D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D003850:Deoxyribonuclease I