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Activating signal cointegrator 2 belongs to a novel steady-state complex that contains a subset of trithorax group proteins.

Many transcription coactivators interact with nuclear receptors in a ligand- and C-terminal transactivation function (AF2)-dependent manner. These include activating signal cointegrator 2 (ASC-2), a recently isolated transcriptional coactivator molecule, which is amplified in human cancers and stimulates transactivation by nuclear receptors and numerous other transcription factors. In this report, we show that ASC-2 belongs to a steady-state complex of approximately 2 MDa (ASC-2 complex [ASCOM]) in HeLa nuclei. ASCOM contains retinoblastoma-binding protein RBQ-3, alpha/beta-tubulins, and trithorax group proteins ALR-1, ALR-2, HALR, and ASH2. In particular, ALR-1/2 and HALR contain a highly conserved 130- to 140-amino-acid motif termed the SET domain, which was recently implicated in histone H3 lysine-specific methylation activities. Indeed, recombinant ALR-1, HALR, and immunopurified ASCOM exhibit very weak but specific H3-lysine 4 methylation activities in vitro, and transactivation by retinoic acid receptor appears to involve ligand-dependent recruitment of ASCOM and subsequent transient H3-lysine 4 methylation of the promoter region in vivo. Thus, ASCOM may represent a distinct coactivator complex of nuclear receptors. Further characterization of ASCOM will lead to a better understanding of how nuclear receptors and other transcription factors mediate transcriptional activation.

Pubmed ID: 12482968


  • Goo YH
  • Sohn YC
  • Kim DH
  • Kim SW
  • Kang MJ
  • Jung DJ
  • Kwak E
  • Barlev NA
  • Berger SL
  • Chow VT
  • Roeder RG
  • Azorsa DO
  • Meltzer PS
  • Suh PG
  • Song EJ
  • Lee KJ
  • Lee YC
  • Lee JW


Molecular and cellular biology

Publication Data

January 16, 2003

Associated Grants


Mesh Terms

  • Amino Acid Motifs
  • Amino Acid Sequence
  • Animals
  • Carrier Proteins
  • Cation Transport Proteins
  • Cell Nucleus
  • DNA-Binding Proteins
  • Drosophila Proteins
  • HeLa Cells
  • Histones
  • Humans
  • Intracellular Signaling Peptides and Proteins
  • Lysine
  • Macromolecular Substances
  • Methylation
  • Molecular Sequence Data
  • Nuclear Proteins
  • Nuclear Receptor Coactivators
  • Receptors, Retinoic Acid
  • Saccharomyces cerevisiae Proteins
  • Sequence Homology, Amino Acid
  • Transcription Factors
  • Tubulin