Temporal and spatial parameters of skeletal gene expression: targeting RUNX factors and their coregulatory proteins to subnuclear domains
Graduate School of Biomedical Sciences; Department of Cell Biology
Medical Subject Headings
Animals; Calcification, Physiologic; Core Binding Factor Alpha 1 Subunit; Core Binding Factor alpha Subunits; Humans; Mice; *Neoplasm Proteins; Nuclear Matrix; Nuclear Matrix-Associated Proteins; *Osteogenesis; *Protein Structure, Tertiary; Time Factors; Transcription Factors; *Transcription, Genetic
Life Sciences | Medicine and Health Sciences
Key components of the basal transcription machinery and several tissue-specific transcription factor complexes are functionally compartmentalized as specialized subnuclear domains. We have identified a unique 31-38 amino acid targeting signal (NMTS) that directs the Runx (Cbfa/AML) transcription factors to distinct nuclear matrix-(NM) associated sites within the nucleus that support gene expression. Our determination of the NMTS crystal structure, yeast 2 hybrid screens to identify NM interacting proteins, and in situ colocalization studies with Runx interacting factors (YAP, Smad, TLE) suggest that localization of Runx transcription factors at intranuclear sites facilitates the assembly and activity of regulatory complexes that mediate activation and suppression of target genes. Mice homozygous for the deletion of the intranuclear Runx2 targeting signal in a homologous recombination (Runx2 deltaC) do not form bone due to maturational arrest of osteoblasts, demonstrating the importance of fidelity of subnuclear localization for tissue-differentiating activity. These results provide evidence that Runx2 subnuclear targeting and the associated regulatory functions are essential for a spatiotemporal placement that facilitates activation of Runx-dependent genes involved in tissue differentiation during embryonic development.
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Citation: Connect Tissue Res. 2003;44 Suppl 1:149-53.