c-Myc/Max heterodimers bind cooperatively to the E-box sequences located in the first intron of the rat ornithine decarboxylase (ODC) gene.
The oncoprotein c-Myc plays an important role in cell proliferation, transformation, inhibition of differentiation and apoptosis. These functions most likely result from the transcription factor activity of c-Myc. As a heterodimer with Max, the c-Myc protein binds to the E-box sequence (CACGTG), which is also recognized by USF dimers. In order to test differences in target gene recognition of c-Myc/Max, Max and USF dimers, we compared the DNA binding characteristics of these proteins in vitro using vaccinia viruses expressing full-length c-Myc and Max proteins. As expected, purified c-Myc/max binds specifically to a consensus E-box. The optimal conditions for DNA binding by either c-Myc/Max, Max or USF dimers differ with respect to ionic strength and Mg2+ ion concentration. Most interestingly, the c-Myc/Max complex binds with a high affinity to its natural target, the rat ODC gene, which contains two adjacent, consensus E-boxes. High affinity binding results from teh ability of c-Myc/Max dimers to bind cooperatively to these E-boxes. We propose that differential cooperative binding by E-box binding transcription factors could contribute to target gene specificity.
Walhout
A J
AJ
Laboratory for Physiological Chemistry, Utrecht University, PO Box 80042, 3508 TA Utrecht, The Netherlands.
Gubbels
J M
JM
Bernards
R
R
van der Vliet
P C
PC
Timmers
H T
HT
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D050976:Basic-Leucine Zipper Transcription Factors; D001665:Binding Sites; D003001:Cloning, Molecular; D018983:DNA Footprinting; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000302:isolation & purification / Q000378:metabolism*; D003850:Deoxyribonuclease I; D019281:Dimerization; D004926:Escherichia coli; D006801:Humans; D007438:Introns; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D009955:Ornithine Decarboxylase / Q000235:genetics*; D016133:Polymerase Chain Reaction; D055503:Protein Multimerization; D016271:Proto-Oncogene Proteins c-myc / Q000302:isolation & purification / Q000378:metabolism*; D051381:Rats; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*
D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D050976:Basic-Leucine Zipper Transcription Factors; D017931:DNA Primers; D004268:DNA-Binding Proteins; C499330:MAX protein, human; C499329:Max protein, rat; C067850:Myc associated factor X; D016271:Proto-Oncogene Proteins c-myc; D011994:Recombinant Proteins; D014157:Transcription Factors; D003850:Deoxyribonuclease I; D009955:Ornithine Decarboxylase