PIAS1 regulates CP2c localization and active promoter complex formation in erythroid cell-specific alpha-globin expression

Nucleic Acids Res. 2010 Sep;38(16):5456-71. doi: 10.1093/nar/gkq286. Epub 2010 Apr 26.


Data presented here extends our previous observations on α-globin transcriptional regulation by the CP2 and PIAS1 proteins. Using RNAi knockdown, we have now shown that CP2b, CP2c and PIAS1 are each necessary for synergistic activation of endogenous α-globin gene expression in differentiating MEL cells. In this system, truncated PIAS1 mutants lacking the ring finger domain recruited CP2c to the nucleus, as did wild-type PIAS1, demonstrating that this is a sumoylation-independent process. In vitro, recombinant CP2c, CP2b and PIAS1 bound DNA as a stable CBP (CP2c/CP2b/PIAS1) complex. Following PIAS1 knockdown in MEL cells, however, the association of endogenous CP2c and CP2b with the α-globin promoter simultaneously decreased. By mapping the CP2b- and CP2c-binding domains on PIAS1, and the PIAS1-binding domains on CP2b and CP2c, we found that two regions of PIAS1 that interact with CP2c/CP2b are required for its co-activator function. We propose that CP2c, CP2b, and PIAS1 form a hexametric complex with two units each of CP2c, CP2b, and PIAS1, in which PIAS1 serves as a clamp between two CP2 proteins, while CP2c binds directly to the target DNA and CP2b mediates strong transactivation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line
  • Cell Line, Tumor
  • Cell Nucleus / metabolism
  • DNA-Binding Proteins / antagonists & inhibitors
  • DNA-Binding Proteins / chemistry
  • DNA-Binding Proteins / metabolism*
  • Erythroid Cells / metabolism*
  • Humans
  • Mice
  • Promoter Regions, Genetic
  • Protein Inhibitors of Activated STAT / antagonists & inhibitors
  • Protein Inhibitors of Activated STAT / chemistry
  • Protein Inhibitors of Activated STAT / metabolism*
  • Protein Interaction Domains and Motifs
  • RNA Interference
  • Transcription Factors / antagonists & inhibitors
  • Transcription Factors / chemistry
  • Transcription Factors / metabolism*
  • Transcriptional Activation*
  • alpha-Globins / genetics*


  • DNA-Binding Proteins
  • Protein Inhibitors of Activated STAT
  • Tfcp2 protein, mouse
  • Transcription Factors
  • alpha-Globins