Activation of p53 transcriptional activity by SMRT: a histone deacetylase 3-independent function of a transcriptional corepressor

Mol Cell Biol. 2014 Apr;34(7):1246-61. doi: 10.1128/MCB.01216-13. Epub 2014 Jan 21.


The silencing mediator of retinoic acid and thyroid hormone receptors (SMRT) is an established histone deacetylase 3 (HDAC3)-dependent transcriptional corepressor. Microarray analyses of MCF-7 cells transfected with control or SMRT small interfering RNA revealed SMRT regulation of genes involved in DNA damage responses, and the levels of the DNA damage marker γH2AX as well as poly(ADP-ribose) polymerase cleavage were elevated in SMRT-depleted cells treated with doxorubicin. A number of these genes are established p53 targets. SMRT knockdown decreased the activity of two p53-dependent reporter genes as well as the expression of p53 target genes, such as CDKN1A (which encodes p21). SMRT bound directly to p53 and was recruited to p53 binding sites within the p21 promoter. Depletion of GPS2 and TBL1, components of the SMRT corepressor complex, but not histone deacetylase 3 (HDAC3) decreased p21-luciferase activity. p53 bound to the SMRT deacetylase activation domain (DAD), which mediates HDAC3 binding and activation, and HDAC3 could attenuate p53 binding to the DAD region of SMRT. Moreover, an HDAC3 binding-deficient SMRT DAD mutant coactivated p53 transcriptional activity. Collectively, these data highlight a biological role for SMRT in mediating DNA damage responses and suggest a model where p53 binding to the DAD limits HDAC3 interaction with this coregulator, thereby facilitating SMRT coactivation of p53-dependent gene expression.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cyclin-Dependent Kinase Inhibitor p21 / genetics
  • Cyclin-Dependent Kinase Inhibitor p21 / metabolism
  • DNA Damage
  • Gene Knockdown Techniques
  • Histone Deacetylases / metabolism*
  • Humans
  • MCF-7 Cells
  • Models, Biological
  • Mutation
  • Nuclear Receptor Co-Repressor 2 / antagonists & inhibitors
  • Nuclear Receptor Co-Repressor 2 / genetics
  • Nuclear Receptor Co-Repressor 2 / metabolism*
  • Promoter Regions, Genetic
  • Protein Binding
  • Protein Interaction Domains and Motifs
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Transcriptional Activation
  • Tumor Suppressor Protein p53 / chemistry
  • Tumor Suppressor Protein p53 / genetics
  • Tumor Suppressor Protein p53 / metabolism*


  • CDKN1A protein, human
  • Cyclin-Dependent Kinase Inhibitor p21
  • NCOR2 protein, human
  • Nuclear Receptor Co-Repressor 2
  • RNA, Messenger
  • Recombinant Fusion Proteins
  • TP53 protein, human
  • Tumor Suppressor Protein p53
  • Histone Deacetylases
  • histone deacetylase 3