Interaction of PIMT with Transcriptional Coactivators CBP, p300, and PBP Differential Role in Transcriptional Regulation

• Published in: The Journal of biological chemistry 2002-05, Vol.277 (22), p.20011-20019
• Main Authors: Misra, Parimal, Qi, Chao, Yu, Songtao, Shah, Sejal H., Cao, Wen-Qing, Rao, M. Sambasiva, Thimmapaya, Bayar, Zhu, Yijun, Reddy, Janardan K.
• Format: Article
• Language: English
• Subjects: Adenoviridae - genetics; Animals; Blotting, Western; Carrier Proteins - chemistry; Carrier Proteins - metabolism; CBP/p300 protein; COS Cells; CREB-Binding Protein; Flow Cytometry; Glutathione Transferase - metabolism; Mediator Complex Subunit 1; Methyltransferases - chemistry; Methyltransferases - metabolism; Microscopy, Fluorescence; Models, Biological; Nuclear Proteins - metabolism; PBP protein; PIMT protein; Plasmids - metabolism; Precipitin Tests; PRIP protein; Protein Binding; Protein D-Aspartate-L-Isoaspartate Methyltransferase; Protein Structure, Tertiary; Recombinant Fusion Proteins - metabolism; RNA-Binding Proteins - chemistry; RNA-Binding Proteins - metabolism; S-adenosylmethionine; Trans-Activators - metabolism; Transcription Factors; Transcription, Genetic; Transcriptional Activation
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M201739200

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-1α 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 PPARγ, as it did for PRIP, indicating synergism between PIMT and PBP. In contrast, PIMT functioned as a repressor of CBP/p300-mediated transactivation of PPARγ. 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.