The cleidocranial dysplasia-related R131G mutation in the Runt-related transcription factor RUNX2 disrupts binding to DNA but not CBF-β

Department of Biochemistry and Cell Biology, School of Medicine, WCU Program, Cell and Matrix Research Institute, Kyungpook National University, Daegu 700-422, South Korea.
Journal of Cellular Biochemistry (Impact Factor: 3.37). 01/2010; 110(1):97-103. DOI: 10.1002/jcb.22516
Source: PubMed

ABSTRACT Cleidocranial dysplasia (CCD) is caused by haploinsufficiency in RUNX2 function. We have previously identified a series of RUNX2 mutations in Korean CCD patients, including a novel R131G missense mutation in the Runt-homology domain. Here, we examine the functional consequences of the RUNX2(R131G) mutation, which could potentially affect DNA binding, nuclear localization signal, and/or heterodimerization with core-binding factor-beta (CBF-beta). Immunofluorescence microscopy and western blot analysis with subcellular fractions show that RUNX2(R131G) is localized in the nucleus. Immunoprecipitation analysis reveals that heterodimerization with CBF-beta is retained. However, precipitation assays with biotinylated oligonucleotides and reporter gene assays with RUNX2 responsive promoters together reveal that DNA-binding activity and consequently the transactivation of potential of RUNX2(R131G) is abrogated. We conclude that loss of DNA binding, but not nuclear localization or CBF-beta heterodimerization, causes RUNX2 haploinsufficiency in patients with the RUNX2(R131G) mutation. Retention of specific functions including nuclear localization and binding to CBF-beta of the RUNX2(R131G) mutation may render the mutant protein an effective competitor that interferes with wild-type function.

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