Id4 dependent acetylation restores mutant-p53 transcriptional activity

Ashley E Knowell,Derrick J Morton,Shanora Glymph,Jaideep Chaudhary,Divya Patel,Pankaj Sharma

doi:10.1186/1476-4598-12-161

Ashley E Knowell, Derrick J Morton + Show 4 more

Open Access

https://doi.org/10.1186/1476-4598-12-161

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Abstract

BackgroundThe mechanisms that can restore biological activity of mutant p53 are an area of high interest given that mutant p53 expression is observed in one third of prostate cancer. Here we demonstrate that Id4, an HLH transcriptional regulator and a tumor suppressor, can restore the mutant p53 transcriptional activity in prostate cancer cells.MethodsId4 was over-expressed in prostate cancer cell line DU145 harboring mutant p53 (P223L and V274F) and silenced in LNCaP cells with wild type p53. The cells were used to quantitate apoptosis, p53 localization, p53 DNA binding and transcriptional activity. Immuno-precipitation/-blot studies were performed to demonstrate interactions between Id4, p53 and CBP/p300 and acetylation of specific lysine residues within p53.ResultsEctopic expression of Id4 in DU145 cells resulted in increased apoptosis and expression of BAX, PUMA and p21, the transcriptional targets of p53. Mutant p53 gained DNA binding and transcriptional activity in the presence of Id4 in DU145 cells. Conversely, loss of Id4 in LNCaP cells abrogated wild type p53 DNA binding and transactivation potential. Gain of Id4 resulted in increased acetylation of mutant p53 whereas loss of Id4 lead to decreased acetylation in DU145 and LNCaP cells respectively. Id4 dependent acetylation of p53 was in part due to a physical interaction between Id4, p53 and acetyl-transferase CBP/p300.ConclusionsTaken together, our results suggest that Id4 regulates the activity of wild type and mutant p53. Id4 promoted the assembly of a macromolecular complex involving CBP/P300 that resulted in acetylation of p53 at K373, a critical post-translational modification required for its biological activity.

Highlights

Id (Inhibitor of differentiation) proteins (Id1, Id2, Id3 and Id4) are dominant negative regulators of basic helix loop helix transcription factors such as TCF3 [1,2]
Generation of Id4 expressing and non-expressing prostate cancer cell lines Id4 is undetectable in DU145 cells due to promoter hyper-methylation [18]
The global acetylation promoted by Id4 suggests that additional lysines such as K120 and K164, known to increase binding to specific p53 responsive genes such as PUMA could be involved, but remains to be investigated

Summary

Introduction

Id (Inhibitor of differentiation) proteins (Id1, Id2, Id3 and Id4) are dominant negative regulators of basic helix loop helix transcription factors such as TCF3 [1,2]. The non-bHLH interaction partners for Id4 are not known. Id proteins can control many cellular processes such as cell growth, differentiation, and apoptosis [3], through specific bHLH and non-bHLH interactions. Id4 promotes differentiation of osteoblasts [4], adipocytes [5], neurons [6], but inhibits oligodendroglial differentiation [7] by blocking the transcriptional activity of bHLH protein Olig1/2. The mechanisms that can restore biological activity of mutant p53 are an area of high interest given that mutant p53 expression is observed in one third of prostate cancer. We demonstrate that Id4, an HLH transcriptional regulator and a tumor suppressor, can restore the mutant p53 transcriptional activity in prostate cancer cells

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