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The p23 molecular chaperone and GCN5 acetylase jointly modulate protein-DNA dynamics and open chromatin status.

ABSTRACT: Cellular processes function through multistep pathways that are reliant on the controlled association and disassociation of sequential protein complexes. While dynamic action is critical to propagate and terminate work, the mechanisms used to disassemble biological structures are not fully understood. Here we show that the p23 molecular chaperone initiates disassembly of protein-DNA complexes and that the GCN5 acetyltransferase prolongs the dissociated state through lysine acetylation. By modulating the DNA-bound state, we found that the conserved and essential joint activities of p23 and GCN5 impacted transcription factor activation potential and response time to an environmental cue. Notably, p23 and GCN5 were required to maintain open chromatin regions along the genome, indicating that dynamic protein behavior is a critical feature of various DNA-associated events. Our data support a model in which p23 and GCN5 regulate diverse multistep pathways by controlling the longevity of protein-DNA complexes.

SUBMITTER: Zelin E

PROVIDER: S-EPMC3496002 | biostudies-literature | 2012 Nov

REPOSITORIES: biostudies-literature

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The p23 molecular chaperone and GCN5 acetylase jointly modulate protein-DNA dynamics and open chromatin status.

Zelin Elena E Zhang Yang Y Toogun Oyetunji A OA Zhong Sheng S Freeman Brian C BC

Molecular cell 20120927 3

Cellular processes function through multistep pathways that are reliant on the controlled association and disassociation of sequential protein complexes. While dynamic action is critical to propagate and terminate work, the mechanisms used to disassemble biological structures are not fully understood. Here we show that the p23 molecular chaperone initiates disassembly of protein-DNA complexes and that the GCN5 acetyltransferase prolongs the dissociated state through lysine acetylation. By modula ...[more]

PMID: 23022381

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Project description:Prostate cancer is an androgen receptor (AR)-dependent malignancy at initiation and progression, therefore hormone therapy is the primary line of systemic treatment. Despite initial disease regression, tumours inevitably recur and progress to an advanced castration-resistant state a major feature of which is metastasis to the bone. Up-regulation of AR cofactors and chaperones that overcome low hormone conditions to maintain basal AR activity has been postulated as a mechanism of therapy relapse. p23, an essential component of the apo-AR complex, acts also after ligand binding to increase AR transcriptional activity and target gene expression, partly by increasing chromatin-loaded holo-receptor-complexes. Immunohistochemical studies have demonstrated increased p23 expression in advanced prostate cancer. Here, we further characterise p23 roles in AR signalling and show that it modulates cytosolic AR levels in the absence of hormone, confirming a chaperoning function in the aporeceptor complex and suggesting p23 upregulates AR signalling at multiple stages. Moreover, p23 protein levels significantly increased upon treatment with not only androgen but also clinically relevant anti-androgens. This was in contrast to the HSP90 inhibitor 17-AAG, which did not modulate expression of the cochaperone - important given the HSP90-independent roles we and others have previously described for p23. Further, we demonstrate p23 is implicated in prostate cancer cell motility and in acquisition of invasiveness capacity through the expression of specific genes known to participate in cancer progression. This may drive metastatic processes in vivo since analysis of prostate tumour biopsies revealed that high nuclear p23 significantly correlated with shorter survival times and with development of metastases in patients with lower grade tumours. We propose that increased p23 expression may allow cells to acquire a more aggressive phenotype, contributing to disease progression, and that p23 is a plausible secondary target in combination with HSP90 inhibition as a potential therapy for advanced prostate cancer.

Project description:To investigate chromatin organization dynamics during the transition from vegetative growth to meiosis, we used Formaldehyde-Assisted Isolation of Regulatory Elements (FAIRE) in vegetative cells (YPD) and in cells undergoing synchronous meiosis/sporulation in the budding yeast Saccharomyces cerevisiae. There is growing recognition that the binding of a transcription factor near a gene does not always indicate regulatory function, and further that a single factor may function to either activate or repress its targets depending on the cellular context. We examined these issues through a series of experiments involving the S. cerevisiae transcription factor Rap1, and its function throughout critical metabolic and developmental transitions between vegetative growth, respiratory growth, meiosis and sporulation. We simultaneously monitored the expression of all genes and the genomic binding locations of Rap1 throughout the timecourse. Genes downstream of Rap1 binding were activated and repressed dynamically, but a change - or lack of change - in Rap1 binding status was not predictive of activation, repression, or no change in regulation. Despite this, we show that Rap1 is required, at a given point in time, for both activation and repression of different gene targets, within the same cell. Specification of the transcriptional consequences of Rap1 binding is thus highly promoter-specific. The presence of other transcription factor binding motifs, the subtype of Rap1 motif, and the underlying chromatin structure of the promoter cannot fully account for the observed transcriptional outcomes. There is a better accounting for the dynamic binding behavior of Rap1 including specification of an expanded meiotic target set through a Tup1- dependent nucleosome-loss mechanism. The variable and dynamic association between binding and transcription in this simple unicellular system portends a similarly volatile relationship in more complex eukaryotes. Biological interpretations of transcription factor occupancy should be made cautiously and in conjunction with supporting data obtained under the precise condition of interest. SK1 yeast strain SHy002 (MATa/MATÎ± ho::LYS2/ho::LYS2 leu2::hisG/leu2::hisG lys2/lys2 ura3/ura3). Meiosis timecourse with samples collected during vegetative growth (YPD), and 0 hr, 1.5hr, and 3hr after transfer to sporulation media (SM). 3 separate biological replicates were used for each condition/time-point. Labeled FAIRE enriched DNA from each sample and a labeled genomic DNA common reference were competitively hybridized to Agilent yeast whole genome 4 x 44k tiling microarrays (resolution ~270bp). The Rap1 ChIP, RNA abundance/expression analysis, and FAIRE analysis were all carried out on the same biological samples. The three FAIRE timecourse replicates correspond to timecourse replicates 1, 4, and 6.

Dataset Information

The p23 molecular chaperone and GCN5 acetylase jointly modulate protein-DNA dynamics and open chromatin status.

Publications

The p23 molecular chaperone and GCN5 acetylase jointly modulate protein-DNA dynamics and open chromatin status.

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