Miz1, a novel zinc finger transcription factor that interacts with Msx2 and enhances its affinity for DNA.
Msx2 is a homeobox gene with a regulatory role in inductive tissue interactions, including those that pattern the skull. We demonstrated previously that individuals affected with an autosomal dominant disorder of skull morphogenesis (craniosynostosis, Boston type) bear a mutated form of Msx2 in which a histidine is substituted for a highly conserved proline in position 7 of the N-terminal arm of the homeodomain (p148h). The mutation behaves as a dominant positive in transgenic mice. The location of the mutation in the N-terminal arm of the homeodomain, a region which in other homeodomain proteins plays a key part in protein-protein interactions, prompted us to undertake a yeast two hybrid screen for Msx2-interacting proteins. Here we present a functional analysis of one such protein, designated Miz1 (Msx-interacting-zinc finger). Miz1 is a zinc finger-containing protein whose amino acid sequence closely resembles that of the yeast protein, Nfi-1. Together these proteins define a new, highly conserved protein family. Analysis of Miz1 expression by Northern blot and in situ hybridization revealed a spatiotemporal pattern that overlaps that of Msx2. Further, Miz1 is a sequence specific DNA binding protein, and it can function as a positive-acting transcription factor. Miz1 interacts directly with Msx2 in vitro and enhances the DNA binding affinity of Msx2 for a functionally important element in the rat osteocalcin promoter. The p148h mutation in Msx2 augments the Miz1 effect on Msx2 DNA binding, suggesting a reason why this mutation behaves in vivo as a dominant positive, and providing a potential explanation of the craniosynostosis phenotype.
Wu
L
L
Department of Biochemistry and Molecular Biology, USC Norris Cancer Hospital and Research Institute, University of Southern California School of Medicine, Los Angeles 90033, USA.
Wu
H
H
Ma
L
L
Sangiorgi
F
F
Wu
N
N
Bell
J R
JR
Lyons
G E
GE
Maxson
R
R
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D004271:DNA, Fungal / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D005809:Genes, Regulator; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D051741:Kruppel-Like Transcription Factors; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D051381:Rats; D012441:Saccharomyces cerevisiae; D016415:Sequence Alignment; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D016335:Zinc Fingers
D004271:DNA, Fungal; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D051741:Kruppel-Like Transcription Factors; C084119:MSX2 protein; D014157:Transcription Factors; C107961:ZBTB17 protein, human