A specific targeting signal directs Runx2/Cbfa1 to subnuclear domains and contributes to transactivation of the osteocalcin gene.
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.
Zaidi
S K
SK
Department of Cell Biology and Cancer Center, University of Massachusetts Medical School, Worcester, MA 01655-0106, USA.
Javed
A
A
Choi
J Y
JY
van Wijnen
A J
AJ
Stein
J L
JL
Lian
J B
JB
Stein
G S
GS
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D015153:Blotting, Western; D002467:Cell Nucleus / Q000378:metabolism*; D050659:Core Binding Factor Alpha 1 Subunit; D004268:DNA-Binding Proteins; D005656:Fungal Proteins / Q000378:metabolism; D017930:Genes, Reporter; D006367:HeLa Cells; D006801:Humans; D017403:In Situ Hybridization; D008156:Luciferases / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D009154:Mutation; D009363:Neoplasm Proteins; D015675:Osteocalcin / Q000235:genetics* / Q000378:metabolism*; D010957:Plasmids / Q000378:metabolism; D017434:Protein Structure, Tertiary; D051381:Rats; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured
D050659:Core Binding Factor Alpha 1 Subunit; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C052130:GAL4 protein, S cerevisiae; D009363:Neoplasm Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D015675:Osteocalcin; D008156:Luciferases