A specific targeting signal directs Runx2/Cbfa1 to subnuclear domains and contributes to transactivation of the osteocalcin gene

• Published in: Journal of cell science Vol. 114; no. Pt 17; pp. 3093 - 3102
• Main Authors: Zaidi, S K, Javed, A, Choi, J Y, van Wijnen, A J, Stein, J L, Lian, J B, Stein, G S
• Format: Journal Article
• Language: English
• Published: England 01.09.2001
• Subjects: Amino Acid Sequence; Animals; Binding Sites; Blotting, Western; Cbfa1 protein; Cell Nucleus - metabolism; Core Binding Factor Alpha 1 Subunit; DNA-Binding Proteins; Fungal Proteins - metabolism; Genes, Reporter; HeLa Cells; Humans; In Situ Hybridization; Luciferases - metabolism; Microscopy, Fluorescence; Molecular Sequence Data; Mutation; Neoplasm Proteins; Osteocalcin - genetics; Osteocalcin - metabolism; Plasmids - metabolism; Protein Structure, Tertiary; Rats; Runx2 protein; Saccharomyces cerevisiae Proteins; Sequence Homology, Amino Acid; Signal Transduction; Transcription Factors - chemistry; Transcription Factors - genetics; Transcription Factors - metabolism; Transcription, Genetic; Transcriptional Activation; Tumor Cells, Cultured
• ISSN: 0021-9533; 1477-9137
• DOI: 10.1242/jcs.114.17.3093

Key components of DNA replication and the basal transcriptional machinery as well as several tissue-specific transcription factors are compartmentalized in specialized nuclear domains. In the present study, we show that determinants of subnuclear targeting of the bone-related Runx2/Cbfa1 protein reside in the C-terminus. With a panel of C-terminal mutations, we further demonstrate that targeting of Runx2 to discrete subnuclear foci is mediated by a 38 amino acid sequence (aa 397-434). This nuclear matrix-targeting signal (NMTS) directs the heterologous Gal4 protein to nuclear-matrix-associated Runx2 foci and enhances transactivation of a luciferase gene controlled by Gal4 binding sites. Importantly, we show that targeting of Runx2 to the NM-associated foci contributes to transactivation of the osteoblast-specific osteocalcin gene in osseous cells. Taken together, these findings identify a critical component of the mechanisms mediating Runx2 targeting to subnuclear foci and provide functional linkage between subnuclear organization of Runx2 and bone-specific transcriptional control.