Two functionally identical modular enhancers in Drosophila troponin T gene establish the correct protein levels in different muscle types.
The control of muscle-specific expression is one of the principal mechanisms by which diversity is generated among muscle types. In an attempt to elucidate the regulatory mechanisms that control fiber diversity in any given muscle, we have focused our attention on the transcriptional regulation of the Drosophila Troponin T gene. Two, nonredundant, functionally identical, enhancer-like elements activate Troponin T transcription independently in all major muscles of the embryo and larvae as well as in adult somatic and visceral muscles. Here, we propose that the differential but concerted interaction of these two elements underlies the mechanism by which a particular muscle-type establish the correct levels of Troponin T expression, adapting these levels to their specific needs. This mechanism is not exclusive to the Troponin T gene, but is also relevant to the muscle-specific Troponin I gene. In conjunction with in vivo transgenic studies, an in silico analysis of the Troponin T enhancer-like sequences revealed that both these elements are organized in a modular manner. Extending this analysis to the Troponin I and Tropomyosin regulatory elements, the two other components of the muscle-regulatory complex, we have discovered a similar modular organization of phylogenetically conserved domains.
Mas
José-Antonio
JA
Departamento de Bioquímica and Instituto de Investigaciones Biomédicas, Facultad de Medicina, Universidad Autonoma de Madrid, UAM-CSIC, 28029 Madrid, Spain.
García-Zaragoza
Elena
E
Cervera
Margarita
M
D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D015153:Blotting, Western; D002461:Cell Line, Transformed; D003001:Cloning, Molecular; D004330:Drosophila; D004331:Drosophila melanogaster; D004591:Electrophoresis, Polyacrylamide Gel; D004742:Enhancer Elements, Genetic; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D015151:Immunoblotting; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009132:Muscles / Q000378:metabolism*; D010802:Phylogeny; D010957:Plasmids / Q000378:metabolism; D017434:Protein Structure, Tertiary; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012689:Sequence Homology, Nucleic Acid; D013909:Thorax / Q000378:metabolism; D013997:Time Factors; D014158:Transcription, Genetic; D019076:Transgenes; D014335:Tropomyosin / Q000235:genetics*; D020107:Troponin T / Q000235:genetics*; D001616:beta-Galactosidase / Q000378:metabolism
D014335:Tropomyosin; D020107:Troponin T; D001616:beta-Galactosidase