Abstract
We have previously demonstrated that important regulatory elements responsible for regulated expression of the human GLUT4 promoter are located between -1154 and -412 relative to transcription initiation (Olson, A. L., and Pessin, J. E. (1995) J. Biol. Chem. 270, 23491-23495). Through further analysis of this promoter regulatory region, we have identified a perfectly conserved myocyte enhancer factor 2 (MEF2)-binding domain (-CTAAAAATAG-) that is necessary, but not sufficient, to support tissue-specific expression of a chloramphenicol acetyltransferase reporter gene in transgenic mice. Biochemical analysis of this DNA element demonstrated the formation of a specific DNA-protein complex using nuclear extracts isolated from heart, hindquarter skeletal muscle, and adipose tissue but not from liver. DNA binding studies indicated that this element functionally interacted with the MEF2A and/or MEF2C MADS family of DNA binding transcription factors. MEF2 DNA binding activity was substantially reduced in nuclear extracts isolated from both heart and skeletal muscle of diabetic mice, which correlated with decreased transcription rate of the GLUT4 gene. MEF2 binding activity completely recovered to control levels following insulin treatment. Together these data demonstrated that MEF2 binding activity is necessary for regulation of the GLUT4 gene promoter in muscle and adipose tissue.
Highlights
We have previously demonstrated that important regulatory elements responsible for regulated expression of the human GLUT4 promoter are located between ؊1154 and ؊412 relative to transcription initiation
The transgenic CAT and endogenous murine GLUT4 mRNAs were expressed at highest levels in brown adipose tissue and skeletal muscle with slightly lower levels in cardiac muscle followed by white adipose tissue
A construct containing 730 bp of 5Ј-flanking data was able to support expression of the reporter gene in hindquarter skeletal muscle, the levels of expression were low in heart and adipose tissue, and expression was observed in tissues that do not normally express high levels of GLUT4 mRNA
Summary
We have previously demonstrated that important regulatory elements responsible for regulated expression of the human GLUT4 promoter are located between ؊1154 and ؊412 relative to transcription initiation Through further analysis of this promoter regulatory region, we have identified a perfectly conserved myocyte enhancer factor 2 (MEF2)-binding domain (-CTAAAAATAG-) that is necessary, but not sufficient, to support tissue-specific expression of a chloramphenicol acetyltransferase reporter gene in transgenic mice. Biochemical analysis of this DNA element demonstrated the formation of a specific DNA-protein complex using nuclear extracts isolated from heart, hindquarter skeletal muscle, and adipose tissue but not from liver. MEF2 binding activity completely recovered to control levels following insulin treatment Together these data demonstrated that MEF2 binding activity is necessary for regulation of the GLUT4 gene promoter in muscle and adipose tissue. The close association of GLUT4 protein pool size with physiologic changes in glucose homeostasis makes physiologic manipulation of GLUT4 gene expression an attractive target for therapeutic interventions designed to treat the insulin resistance associated with diabetes
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
