Synergy among nuclear receptor coactivators: selective requirement for protein methyltransferase and acetyltransferase activities.
Hormone-activated nuclear receptors (NR) bind to specific regulatory DNA elements associated with their target genes and recruit coactivator proteins to remodel chromatin structure, recruit RNA polymerase, and activate transcription. The p160 coactivators (e.g., SRC-1, GRIP1, and ACTR) bind directly to activated NR and can recruit a variety of secondary coactivators. We have established a transient-transfection assay system under which the activity of various NR is highly or completely dependent on synergistic cooperation among three classes of coactivators: a p160 coactivator, the protein methyltransferase CARM1, and any of the three protein acetyltransferases, p300, CBP, or p/CAF. The three-coactivator functional synergy was only observed when low levels of NR were expressed and was highly or completely dependent on the methyltransferase activity of CARM1 and the acetyltransferase activity of p/CAF, but not the acetyltransferase activity of p300. Other members of the protein arginine methyltransferase family, which methylate different protein substrates than CARM1, could not substitute for CARM1 to act synergistically with p300 or p/CAF. A ternary complex of GRIP1, CARM1, and p300 or CBP was demonstrated in cultured mammalian cells, supporting a physiological role for the observed synergy. The transfection assay described here is a valuable new tool for investigating the mechanism of coactivator function and demonstrates the importance of multiple coactivators, including CARM1 and its specific protein methyltransferase activity, in transcriptional activation.
Lee
Young-Ho
YH
Department of Biochemistry and Molecular Biology, University of Southern California, Los Angeles, California 90089, USA.
Koh
Stephen S
SS
Zhang
Xing
X
Cheng
Xiaodong
X
Stallcup
Michael R
MR
D000123:Acetyltransferases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D019556:COS Cells; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D051548:Histone Acetyltransferases; D006801:Humans; D008954:Models, Biological; D051958:Nuclear Receptor Coactivator 2; D011496:Protein Methyltransferases / Q000235:genetics / Q000378:metabolism*; D011484:Protein-Arginine N-Methyltransferases / Q000235:genetics / Q000378:metabolism; D051381:Rats; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation; D014162:Transfection; D050880:p300-CBP Transcription Factors; D000099224:p300-CBP-Associated Factor
D000123:Acetyltransferases; D018797:Cell Cycle Proteins; D051548:Histone Acetyltransferases; D051958:Nuclear Receptor Coactivator 2; D011496:Protein Methyltransferases; D011484:Protein-Arginine N-Methyltransferases; D018160:Receptors, Cytoplasmic and Nuclear; D014157:Transcription Factors; D050880:p300-CBP Transcription Factors; D000099224:p300-CBP-Associated Factor; C498001:NCOA2 protein, human; C498003:Ncoa2 protein, rat; C119966:coactivator-associated arginine methyltransferase 1