Multiple Cbfa/AML sites in the rat osteocalcin promoter are required for basal and vitamin D-responsive transcription and contribute to chromatin organization

Amjad Javed, Soraya Gutierrez, Martin Montecino, Aandré J. Van Wijnen, Janet L. Stein, Gary S. Stein, Jane B. Lian

Resultado de la investigación: Contribución a una revistaArtículorevisión exhaustiva

125 Citas (Scopus)

Resumen

Three Cbfa motifs are strategically positioned in the bone-specific rat osteocalcin (rOC) promoter. Sites A and B flank the vitamin D response element in the distal promoter and sites B and C flank a positioned nucleosome in the proximal promoter. The functional significance of each Cbfa element was addressed by mutating individual or multiple Cbfa sites within the context of the -1.1-kb rOC promoter fused to a chloramphenicol acetyltransferase reporter gene. Promoter activity was assayed following transient transfection and after stable genomic integration in ROS 17/2.8 osteoblastic cell lines. We show that all three Cbfa sites are required for maximal basal expression of the rOC promoter. However, the distal sites A and B each contribute significantly more (P < 0.001) to promoter activity than site C. In a genomic context, sites A and B can largely compensate for a mutation at the proximal site C, and paired mutations involving site A (mAB or mAC) result in a far greater loss of activity than the mBC mutation. Strikingly, mutation of the three Cbfa sites leads to abrogation of responsiveness to vitamin D. Vitamin D-enhanced activity is also not observed when sites A and B are mutated. Significantly, related to these losses in transcriptional activity, mutation of the three Cbfa sites results in altered chromatin structure as reflected by loss of DNase I-hypersensitive sites at the vitamin D response element and over the proximal tissue-specific basal promoter. These findings strongly support a multifunctional role for Cbfa factors in regulating gene expression, not only as simple transcriptional transactivators but also by facilitating modifications in promoter architecture and chromatin organization.

Idioma originalInglés
Páginas (desde-hasta)7491-7500
Número de páginas10
PublicaciónMolecular and Cellular Biology
Volumen19
N.º11
DOI
EstadoPublicada - nov. 1999

Áreas temáticas de ASJC Scopus

  • Biología molecular
  • Biología celular

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