Restricted leucine zipper dimerization and specificity of DNA recognition of the melanocyte master regulator MITF

TY - JOUR

T1 - Restricted leucine zipper dimerization and specificity of DNA recognition of the melanocyte master regulator MITF

AU - Pogenberg, Vivian

AU - Ogmundsdóttir, Margrét H

AU - Bergsteinsdóttir, Kristín

AU - Schepsky, Alexander

AU - Phung, Bengt

AU - Deineko, Viktor

AU - Milewski, Morlin

AU - Steingrímsson, Eiríkur

AU - Wilmanns, Matthias

PY - 2012/12/1

Y1 - 2012/12/1

N2 - Microphthalmia-associated transcription factor (MITF) is a master regulator of melanocyte development and an important oncogene in melanoma. MITF heterodimeric assembly with related basic helix-loop-helix leucine zipper transcription factors is highly restricted, and its binding profile to cognate DNA sequences is distinct. Here, we determined the crystal structure of MITF in its apo conformation and in the presence of two related DNA response elements, the E-box and M-box. In addition, we investigated mouse and human Mitf mutations to dissect the functional significance of structural features. Owing to an unusual three-residue shift in the leucine zipper register, the MITF homodimer shows a marked kink in one of the two zipper helices to allow an out-of-register assembly. Removal of this insertion relieves restricted heterodimerization by MITF and permits assembly with the transcription factor MAX. Binding of MITF to the M-box motif is mediated by an unusual nonpolar interaction by Ile212, a residue that is mutated in mice and humans with Waardenburg syndrome. As several related transcription factors have low affinity for the M-box sequence, our analysis unravels how these proteins discriminate between similar target sequences. Our data provide a rational basis for targeting MITF in the treatment of important hereditary diseases and cancer.

AB - Microphthalmia-associated transcription factor (MITF) is a master regulator of melanocyte development and an important oncogene in melanoma. MITF heterodimeric assembly with related basic helix-loop-helix leucine zipper transcription factors is highly restricted, and its binding profile to cognate DNA sequences is distinct. Here, we determined the crystal structure of MITF in its apo conformation and in the presence of two related DNA response elements, the E-box and M-box. In addition, we investigated mouse and human Mitf mutations to dissect the functional significance of structural features. Owing to an unusual three-residue shift in the leucine zipper register, the MITF homodimer shows a marked kink in one of the two zipper helices to allow an out-of-register assembly. Removal of this insertion relieves restricted heterodimerization by MITF and permits assembly with the transcription factor MAX. Binding of MITF to the M-box motif is mediated by an unusual nonpolar interaction by Ile212, a residue that is mutated in mice and humans with Waardenburg syndrome. As several related transcription factors have low affinity for the M-box sequence, our analysis unravels how these proteins discriminate between similar target sequences. Our data provide a rational basis for targeting MITF in the treatment of important hereditary diseases and cancer.

KW - Amino Acid Sequence

KW - Animals

KW - DNA-Binding Proteins/chemistry

KW - Dimerization

KW - Enhancer Elements, Genetic/genetics

KW - Humans

KW - Leucine Zippers/genetics

KW - Mice

KW - Microphthalmia-Associated Transcription Factor/chemistry

KW - Models, Molecular

KW - Molecular Sequence Data

KW - Mutation

KW - Protein Binding

KW - Protein Structure, Tertiary

KW - Sequence Alignment

KW - Waardenburg Syndrome/genetics

U2 - 10.1101/gad.198192.112

DO - 10.1101/gad.198192.112

M3 - SCORING: Journal article

C2 - 23207919

VL - 26

SP - 2647

EP - 2658

JO - GENE DEV

JF - GENE DEV

SN - 0890-9369

IS - 23

ER -