Mechanisms of MEOX1 and MEOX2 regulation of the cyclin dependent kinase inhibitors p21 and p16 in vascular endothelial cells

PLoS One. 2011;6(12):e29099. doi: 10.1371/journal.pone.0029099. Epub 2011 Dec 20.


Senescence, the state of permanent cell cycle arrest, has been associated with endothelial cell dysfunction and atherosclerosis. The cyclin dependent kinase inhibitors p21(CIP1/WAF1) and p16(INK4a) govern the G(1)/S cell cycle checkpoint and are essential for determining whether a cell enters into an arrested state. The homeodomain transcription factor MEOX2 is an important regulator of vascular cell proliferation and is a direct transcriptional activator of both p21(CIP1/WAF1) and p16(INK4a). MEOX1 and MEOX2 have been shown to be partially functionally redundant during development, suggesting that they regulate similar target genes in vivo. We compared the ability of MEOX1 and MEOX2 to activate p21(CIP1/WAF1) and p16(INK4a) expression and induce endothelial cell cycle arrest. Our results demonstrate for the first time that MEOX1 regulates the MEOX2 target genes p21(CIP1/WAF1) and p16(INK4a). In addition, increased expression of either of the MEOX homeodomain transcription factors leads to cell cycle arrest and endothelial cell senescence. Furthermore, we show that the mechanism of transcriptional activation of these cyclin dependent kinase inhibitor genes by MEOX1 and MEOX2 is distinct. MEOX1 and MEOX2 activate p16(INK4a) in a DNA binding dependent manner, whereas they induce p21(CIP1/WAF1) in a DNA binding independent manner.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Base Sequence
  • Binding Sites
  • Cell Proliferation
  • Cellular Senescence
  • Cyclin-Dependent Kinase Inhibitor p16 / genetics*
  • Cyclin-Dependent Kinase Inhibitor p16 / metabolism*
  • Cyclin-Dependent Kinase Inhibitor p21 / genetics*
  • Cyclin-Dependent Kinase Inhibitor p21 / metabolism*
  • DNA / metabolism
  • Endothelial Cells / cytology
  • Endothelial Cells / metabolism*
  • HEK293 Cells
  • Homeodomain Proteins / metabolism*
  • Human Umbilical Vein Endothelial Cells / cytology
  • Human Umbilical Vein Endothelial Cells / metabolism
  • Humans
  • Intracellular Space / metabolism
  • Mice
  • Promoter Regions, Genetic / genetics
  • Protein Transport
  • Sp1 Transcription Factor / metabolism
  • Transcription Factors
  • Transcription, Genetic
  • Transcriptional Activation


  • Cyclin-Dependent Kinase Inhibitor p16
  • Cyclin-Dependent Kinase Inhibitor p21
  • Homeodomain Proteins
  • MEOX2 protein, human
  • Meox1 protein, mouse
  • Sp1 Transcription Factor
  • Transcription Factors
  • DNA