Communication between the ERRalpha homodimer interface and the PGC-1alpha binding surface via the helix 8-9 loop.
Although structural studies on the ligand-binding domain (LBD) have established the general mode of nuclear receptor (NR)/coactivator interaction, determinants of binding specificity are only partially understood. The LBD of estrogen receptor-alpha (ERalpha), for example, interacts only with a region of peroxisome proliferator-activated receptor coactivator (PGC)-1alpha, which contains the canonical LXXLL motif (NR box2), whereas the LBD of estrogen-related receptor-alpha (ERRalpha) also binds efficiently an untypical, LXXYL-containing region (NR box3) of PGC-1alpha. Surprisingly, in a previous structural study, the ERalpha LBD has been observed to bind NR box3 of transcriptional intermediary factor (TIF)-2 untypically via LXXYL, whereas the ERRalpha LBD binds this region of TIF-2 only poorly. Here we present a new crystal structure of the ERRalpha LBD in complex with a PGC-1alpha box3 peptide. In this structure, residues N-terminal of the PGC-1alpha LXXYL motif formed contacts with helix 4, the loop connecting helices 8 and 9, and with the C terminus of the ERRalpha LBD. Interaction studies using wild-type and mutant PGC-1alpha and ERRalpha showed that these contacts are functionally relevant and are required for efficient ERRalpha/PGC-1alpha interaction. Furthermore, a structure comparison between ERRalpha and ERalpha and mutation analyses provided evidence that the helix 8-9 loop, which differs significantly in both nuclear receptors, is a major determinant of coactivator binding specificity. Finally, our results revealed that in ERRalpha the helix 8-9 loop allosterically links the LBD homodimer interface with the coactivator cleft, thus providing a plausible explanation for distinct PGC-1alpha binding to ERRalpha monomers and homodimers.
Greschik
Holger
H
Département de Biologie et Génomique Structurales, Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.
Althage
Magnus
M
Flaig
Ralf
R
Sato
Yoshiteru
Y
Chavant
Virginie
V
Peluso-Iltis
Carole
C
Choulier
Laurence
L
Cronet
Philippe
P
Rochel
Natacha
N
Schüle
Roland
R
Strömstedt
Per-Erik
PE
Moras
Dino
D
D000595:Amino Acid Sequence; D018360:Crystallography, X-Ray; D019281:Dimerization; D006360:Heat-Shock Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011960:Receptors, Estrogen / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D014157:Transcription Factors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000097983:ERRalpha Estrogen-Related Receptor
D006360:Heat-Shock Proteins; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D011960:Receptors, Estrogen; D014157:Transcription Factors; D000097983:ERRalpha Estrogen-Related Receptor; C486497:PPARGC1A protein, human