Muscle gene E-box control elements. Evidence for quantitatively different transcriptional activities and the binding of distinct regulatory factors.
The muscle creatine kinase gene enhancer contains two regulatory elements (MCK-R and MCK-L) with the consensus E-box sequence (CAnnTG). A myocyte specific protein complex, MEF1, binds the MCK-R site. MEF1 contains several basic H-L-H myogenic determination factors (MDFs), each dimerized with ubiquitous members of the bH-L-H family (e.g. E12/E47). We now demonstrate that the ubiquitous bH-L-H factor E2-2 is a major component of the endogenous MCK-R site specific complex. Previous studies described the MCK-L site as a similar but low affinity MDF/bH-L-H heterodimer binding site. However, we find that the MCK-L site exhibits preferential binding of an unknown ubiquitous factor which contains neither E12/E47 nor E2-2, and that it exhibits differential transcriptional activity with muscle and non-muscle cells. The differential behavior of the MCK-L and MCK-R sites may be a general trait of E-box elements since one among several E-boxes in the MLC 1/3 enhancer also binds preferentially to the MCK-L factor. From our studies we now propose separate consensus sequences for MCK-R and MCK-L E-box types: AACAc/gc/gTGCa/t and GGa/cCANGTGGc/gNa/g. Our results suggest that while many muscle gene E-boxes are capable of binding the previously characterized spectrum of MDF/bH-L-H heterodimers in vitro, MCK-L type E-boxes probably bind qualitatively different factors in vivo.
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Department of Biochemistry SJ-70, University of Washington, Seattle 98195, USA.
Hauschka
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D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002457:Cell Extracts; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D003402:Creatine Kinase / Q000235:genetics* / Q000378:metabolism; D004742:Enhancer Elements, Genetic; D051379:Mice; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000235:genetics* / Q000378:metabolism; D009132:Muscles / Q000166:cytology / Q000378:metabolism; D009838:Oligodeoxyribonucleotides; D051381:Rats; D014158:Transcription, Genetic
D002457:Cell Extracts; D009124:Muscle Proteins; D009838:Oligodeoxyribonucleotides; D003402:Creatine Kinase