Interaction of PIMT with transcriptional coactivators CBP, p300, and PBP differential role in transcriptional regulation.
PIMT (PRIP-interacting protein with methyltransferase domain), an RNA-binding protein with a methyltransferase domain capable of binding S-adenosylmethionine, has been shown previously to interact with nuclear receptor coactivator PRIP (peroxisome proliferator-activated receptor (PPAR)-interacting protein) and enhance its coactivator function. We now report that PIMT strongly interacts with transcriptional coactivators, CBP, p300, and PBP but not with SRC-1 and PGC-1alpha under in vitro and in vivo conditions. The PIMT binding sites on CBP and p300 are located in the cysteine-histidine-rich C/H1 and C/H3 domains, and the PIMT binding site on PBP is in the region encompassing amino acids 1101-1560. The N-terminal of PIMT (residues 1-369) containing the RNA binding domain interacts with both C/H1 and C/H3 domains of CBP and p300 and with the C-terminal portion of PBP that encompasses amino acids 1371-1560. The C-terminal of PIMT (residues 611-852), which binds S-adenosyl-l-methionine, interacts respectively with the C/H3 domain of CBP/p300 and with a region encompassing amino acids 1101-1370 of PBP. Immunoprecipitation data showed that PIMT forms a complex in vivo with CBP, p300, PBP, and PRIP. PIMT appeared to be co-localized in the nucleus with CBP, p300, and PBP. PIMT enhanced PBP-mediated transcriptional activity of the PPARgamma, as it did for PRIP, indicating synergism between PIMT and PBP. In contrast, PIMT functioned as a repressor of CBP/p300-mediated transactivation of PPARgamma. Based on these observations, we suggest that PIMT bridges the CBP/p300-anchored coactivator complex with the PBP-anchored coactivator complex but differentially modulates coactivator function such that inhibition of the CBP/p300 effect may be designed to enhance the activity of PBP and PRIP.
Misra
Parimal
P
Department of Pathology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611-3008, USA.
Qi
Chao
C
Yu
Songtao
S
Shah
Sejal H
SH
Cao
Wen-Qing
WQ
Rao
M Sambasiva
MS
Thimmapaya
Bayar
B
Zhu
Yijun
Y
Reddy
Janardan K
JK
D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D015153:Blotting, Western; D019556:COS Cells; D050882:CREB-Binding Protein; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism*; D005434:Flow Cytometry; D005982:Glutathione Transferase / Q000378:metabolism; D056913:Mediator Complex Subunit 1; D008780:Methyltransferases / Q000737:chemistry / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D009687:Nuclear Proteins / Q000378:metabolism*; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D026601:Protein D-Aspartate-L-Isoaspartate Methyltransferase; D017434:Protein Structure, Tertiary; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors; D014158:Transcription, Genetic; D015533:Transcriptional Activation
D002352:Carrier Proteins; C538855:MED1 protein, human; D056913:Mediator Complex Subunit 1; D009687:Nuclear Proteins; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D008780:Methyltransferases; C435725:PCMT1 protein, human; D026601:Protein D-Aspartate-L-Isoaspartate Methyltransferase; D050882:CREB-Binding Protein; D005982:Glutathione Transferase