p107-Dependent recruitment of SWI/SNF to the alkaline phosphatase promoter during osteoblast differentiation

Bone. 2014 Dec;69:47-54. doi: 10.1016/j.bone.2014.08.009. Epub 2014 Aug 23.

Abstract

The retinoblastoma protein family is intimately involved in the regulation of tissue specific gene expression during mesenchymal stem cell differentiation. The role of the following proteins, pRB, p107 and p130, is particularly significant in differentiation to the osteoblast lineage, as human germ-line mutations of RB1 greatly increase susceptibility to osteosarcoma. During differentiation, pRB directly targets certain osteogenic genes for activation, including the alkaline phosphatase-encoding gene Alpl. Chromatin immunoprecipitation (ChIP) assays indicate that Alpl is targeted by p107 in differentiating osteoblasts selectively during activation with the same dynamics as pRB, which suggests that p107 helps promote Alpl activation. Mouse models indicate overlapping roles for pRB and p107 in bone and cartilage formation, but very little is known about direct tissue-specific gene targets of p107, or the consequences of targeting by p107. Here, the roles of p107 and pRB were compared using shRNA-mediated knockdown genetics in an osteoblast progenitor model, MC3T3-E1 cells. The results show that p107 has a distinct role along with pRB in induction of Alpl. Deficiency of p107 does not impede recruitment of transcription factors recognized as pRB co-activation partners at the promoter; however, p107 is required for the efficient recruitment of an activating SWI/SNF chromatin-remodeling complex, an essential event in Alpl induction.

Keywords: Alpl; Osteoblasts; SWI/SNF; p107; pRB.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Alkaline Phosphatase / biosynthesis*
  • Animals
  • Cell Differentiation / physiology*
  • Chromatin Immunoprecipitation
  • Chromosomal Proteins, Non-Histone / metabolism*
  • Gene Expression Regulation / physiology*
  • Gene Knockdown Techniques
  • Mice
  • Osteoblasts / cytology*
  • Osteoblasts / metabolism
  • Promoter Regions, Genetic
  • Retinoblastoma Protein / metabolism
  • Retinoblastoma-Like Protein p107 / metabolism*
  • Reverse Transcriptase Polymerase Chain Reaction
  • Stem Cells / cytology
  • Stem Cells / metabolism
  • Transcription Factors / metabolism*

Substances

  • Chromosomal Proteins, Non-Histone
  • Retinoblastoma Protein
  • Retinoblastoma-Like Protein p107
  • SWI-SNF-B chromatin-remodeling complex
  • Transcription Factors
  • ALPL protein, mouse
  • Alkaline Phosphatase