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

Parimal Misra,Chao Qi,Songtao Yu,Sejal H Shah,Wen-Qing Cao,M Sambasiva Rao,Bayar Thimmapaya,Yijun Zhu,Janardan K Reddy

doi:10.1074/jbc.m201739200

Abstract

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.

Highlights

The nuclear receptor superfamily consists of several ligandregulated transcription factors that include the steroid and thyroid hormone receptors, vitamin D3 receptor, retinoic acid receptors, and the peroxisome proliferator-activated receptors (PPARs),1 among others [1,2,3]
PIMT Interacts with CREB-binding protein (CBP), p300, PPAR-binding protein (PBP), and PRIP but Not with PGC1 and SRC-1—Previously, we have shown that PIMT interacts with PRIP [41]
Having confirmed that PGC-1␣ and SRC-1 failed to interact with truncated PIMT (PIMTC), we tested the interaction of glutathione S-transferase (GST)-PIMTA and GST-PIMTB with in vitro translated [35S]methionine-labeled full-length SRC-1 and PGC-1␣ (Fig. 1C)

Summary

Introduction

The nuclear receptor superfamily consists of several ligandregulated transcription factors that include the steroid and thyroid hormone receptors, vitamin D3 receptor, retinoic acid receptors, and the peroxisome proliferator-activated receptors (PPARs),1 among others [1,2,3]. We report that PIMT strongly interacts with transcriptional coactivators, CBP, p300, and PBP but not with SRC-1 and PGC-1␣ under in vitro and in vivo conditions.

Results

Conclusion