Book of Abstracts: Albany 2011

category image Albany 2011
Conversation 17
June 14-18 2011
©Adenine Press (2010)

The Mode of DNA Recognition and Dimerization Specificity of MITF Revealed by Three Crystal Structures

The Microphthalmia-associated Transcription Factor (MITF) regulates the expression of pigment-cell specific genes in melanocytes, the mature pigment producing cells of the skin and hair follicles. In addition, MITF function is of major interest in the investigation of the mechanisms leading to melanoma. MITF belongs to the superfamily of basic Helix-Loop-Helix leucine zipper transcription factors (b-HLH-Zip). Like other b-HLH-Zip factors, MITF can bind a subset of the canonical palindromic E-box sequence (CANNTG) as well as related asymmetric motives like M-box (TCATNTG); nevertheless the exact mechanism in which MITF recognizes the correct promoters of target genes is not yet fully understood. Within the b-HLH-Zip family, MITF associates with the Tfe factors, but no heterodimeric complex containing MITF and the related Myc, MAX or USF-1 have been observed, raising the question how this discrimination is achieved. We determined the crystal structure of MITF in its apo form and of two different complexes of MITF with DNA containing two different target motives (E-box and M-box). We pursued the study measuring interactions between these DNA motives and several MITF mutants with known phenotype in mice, using different technique such as using Isothermal Titration Calorimetry, Fluorescence Anisotropy or EMSA. Comparing structural, biophysical and biological data, this study reveals a particular mechanism of DNA recognition by MITF and how MITF discriminates between the E and M boxes. In addition, our data demonstrate an unusual mode of dimerization that might explain how MITF select its heterodimerization partners.

Vivian Pogenberg1*
Viktor Deineko1
Morlin Milewski1
Alexander Schepsky2
Eirikur Steingrimsson2
and Matthias Wilmanns1

1EMBL-Hamburg, c/o DESY, Notkestrasse 85, 22603 Hamburg, Germany
2Department of Biochemistry and Molecular Biology, Faculty of Medecine, University of Iceland, 101 Reykjavik, Iceland