Nucleic Acids Research Advance Access originally published online on October 16, 2007
Nucleic Acids Research 2007 35(21):7087-7095; doi:10.1093/nar/gkm746
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Nucleic Acids Research, 2007, Vol. 35, No. 21 7087-7095
© 2007 The Author(s)
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Molecular Biology |
MyoD uses overlapping but distinct elements to bind E-box and tetraplex structures of regulatory sequences of muscle-specific genes
Department of Biochemistry, Rappaport Faculty of Medicine, Technion – Israel Institute of Technology, POB 9649 Bat Galim, Haifa 31096, Israel
* To whom correspondence should be addressed. Tel: +972 4 829 5328; Fax: +972 4 851 0735; Email: mickey{at}tx.technion.ac.il
Received August 1, 2007. Revised September 6, 2007. Accepted September 9, 2007.
Muscle differentiation and expression of muscle-specific proteins are initiated by the binding of heterodimers of the transcription factor MyoD with E2A proteins to E-box motif d(CANNTG) in promoters or enhancers of muscle-specific genes. MyoD homodimers, however, form tighter complexes with tetraplex structures of guanine-rich regulatory sequences of some muscle genes. In this work, we identified elements in MyoD that bind E-box or tetraplex structures of promoter sequences of the muscle-specific genes 
7 integrin and sarcomeric Mitochondrial Creatine Kinase (sMtCK). Deletions of large domains of the 315 amino acids long recombinant MyoD indicated that the binding site for both E-box and tetraplex DNA is its basic region KRKTTNADRRKAATMRERRR that encompasses the three underlined clusters of basic residues designated R1, R2 and R3. Deletion of a single or pairs of R triads or R111C substitution completely abolished the E-box-binding capacity of MyoD. By contrast, the MyoD deletion mutants 
102–114, R3, R1R3 or R2R3 maintained comparable tetraplex DNA-binding capacity as reflected by the similar dissociation constants of their protein–DNA complexes. Only deletion of all three basic clusters abolished the binding of tetraplex DNA. Implications of the binding of E-box and tetraplex DNA by non-identical MyoD elements are considered.
The authors wish it to be known that, in their opinion, the first two authors should be regarded as joint First Authors