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DNA Binding Specificity of the Basic-Helix-Loop-Helix Protein MASH-1

Meierhans, Daniel, el-Ariss, Chirine, Neuenschwander, Margrit, Sieber, Martin, Stackhouse, Joseph F. and Allemann, Rudolf Konrad ORCID: 1995. DNA Binding Specificity of the Basic-Helix-Loop-Helix Protein MASH-1. Biochemistry 34 (35) , pp. 11026-11036. 10.1021/bi00035a008

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Despite the high degree of sequence similarity in their basic-helix-loop-helix (BHLH) domains, MASH-1 and MyoD are involved in different biological processes. In order to define possible differences between the DNA binding specificities of these two proteins, we investigated the DNA binding properties of MASH- 1 by circular dichroism spectroscopy and by electrophoretic mobility shift assays (EMSA). Upon binding to DNA, the BHLH domain of MASH-1 underwent a conformational change from a mainly unfolded to a largely a-helical form, and surprisingly, this change was independent of the specific DNA sequence. The same conformational transition could be induced by the addition of 20% 2,2,2-trifluoroethanol. The apparent dissociation constants (KD)of the complexes of full-length MASH-1 with various oligonucleotides were determined from half-saturation points in EMSAs. MASH- 1 bound as a dimer to DNA sequences containing an E-box with high affinity (KD = 1.4-4.1 x M2). However, the specificity of DNA binding was low. The dissociation constant for the complex between MASH-1 and the highest affinity E-box sequence (KD = 1.4 x M2) was only a factor of 10 smaller than for completely unrelated DNA sequences (KD = -1 x M2). The DNA binding specificity of MASH-1 was not significantly increased by the formation of an heterodimer with the ubiquitous E12 protein. MASH- 1 and MyoD displayed similar binding site preferences, suggesting that their different target gene specificities cannot be explained solely by differential DNA binding. An explanation for these findings is provided on the basis of the known crystal structure of the BHLH domain of MyoD.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Chemistry
Cardiff Catalysis Institute (CCI)
Subjects: Q Science > QD Chemistry
Publisher: American Chemical Society
ISSN: 0006-2960
Last Modified: 18 Oct 2022 13:19

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