The coactivator TIF2 contains three nuclear receptor-binding motifs and mediates transactivation through CBP binding-dependent and -independent pathways.
The nuclear receptor (NR) coactivator TIF2 possesses a single NR interaction domain (NID) and two autonomous activation domains, AD1 and AD2. The TIF2 NID is composed of three NR-interacting modules each containing the NR box motif LxxLL. Mutation of boxes I, II and III abrogates TIF2-NR interaction and stimulation, in transfected cells, of the ligand-induced activation function-2 (AF-2) present in the ligand-binding domains (LBDs) of several NRs. The presence of an intact NR interaction module II in the NID is sufficient for both efficient interaction with NR holo-LBDs and stimulation of AF-2 activity. Modules I and III are poorly efficient on their own, but synergistically can promote interaction with NR holo-LBDs and AF-2 stimulation. TIF2 AD1 activity appears to be mediated through CBP, as AD1 could not be separated mutationally from the CBP interaction domain. In contrast, TIF2 AD2 activity apparently does not involve interaction with CBP. TIF2 exhibited the characteristics expected for a bona fide NR coactivator, in both mammalian and yeast cells. Moreover, in mammalian cells, a peptide encompassing the TIF2 NID inhibited the ligand-induced AF-2 activity of several NRs, indicating that NR AF-2 activity is either mediated by endogenous TIF2 or by coactivators recognizing a similar surface on NR holo-LBDs.
Voegel
J J
JJ
Institut de Génétique et de Biologie Moléculaire et Cellulaire, (IGBMC)/CNRS/INSERM/ULP/Collège de France, Strasbourg.
Heine
M J
MJ
Tini
M
M
Vivat
V
V
Chambon
P
P
Gronemeyer
H
H
D000595:Amino Acid Sequence; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D004268:DNA-Binding Proteins / Q000502:physiology*; D005656:Fungal Proteins / Q000502:physiology*; D005822:Genetic Vectors / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D051958:Nuclear Receptor Coactivator 2; D017434:Protein Structure, Tertiary; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D015533:Transcriptional Activation / Q000187:drug effects; D014162:Transfection
D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; C064042:CBF1 protein, S cerevisiae; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C498001:NCOA2 protein, human; D009687:Nuclear Proteins; D051958:Nuclear Receptor Coactivator 2; D018160:Receptors, Cytoplasmic and Nuclear; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors