Quantification of C13orf19/P38IP mRNA expression by quantitative real-time PCR in patients with urological malignancies

The promiscuity of the SAGA complex subunits: Multifunctional or moonlighting proteins?

Gene expression, the decoding of DNA information into accessible instructions for protein synthesis, is a complex process in which multiple steps, including transcription, mRNA processing and mRNA export, are regulated by different factors. One of the first steps in this process involves chemical and structural changes in chromatin to allow transcription. For such changes to occur, histone tail and DNA epigenetic modifications foster the binding of transcription factors to promoter regions. The SAGA coactivator complex plays a crucial role in this process by mediating histone acetylation through Gcn5, and histone deubiquitination through Ubp8 enzymes. However, most SAGA subunits interact physically with other proteins beyond the SAGA complex. These interactions could represent SAGA-independent functions or a mechanism to widen SAGA multifunctionality. Among the different mechanisms to perform more than one function, protein moonlighting defines unrelated molecular activities for the same polypeptide sequence. Unlike pleiotropy, where a single gene can affect different phenotypes, moonlighting necessarily involves separate functions of a protein at the molecular level. In this review we describe in detail some of the alternative physical interactions of several SAGA subunits. In some cases, the alternative role constitutes a clear moonlighting function, whereas in most of them the lack of molecular evidence means that we can only define these interactions as promiscuous that require further work to verify if these are moonlighting functions.

A novel miR-200b-3p/p38IP pair regulates monocyte/macrophage differentiation

Monocyte/macrophage differentiation represents a major branch of hematopoiesis and is a central event in the immune response, but the molecular mechanisms underlying are not fully delineated. Here we show that p38 mitogen-activated protein kinase (MAPK) interacting protein (p38IP) is downregulated during monocyte/macrophage differentiation in vitro. Overexpression of p38IP halted monocyte/macrophage differentiation, whereas forward knockdown of p38IP by RNA interference induced G1/S arrest and promoted monocyte differentiation into macrophages and the maturation of macrophages as well. Moreover, we found that miR-200b-3p was upregulated during monocyte/macrophage differentiation and mediated the downregulation of p38IP by binding to the 3′ untranslated terminal region of p38IP mRNA. Overexpression of a miR-200b-3p mimic resembled the effect of p38IP knockdown, whereas a miR-200b-3p inhibitor blocked monocyte/macrophage differentiation by enhancing p38IP expression. Further western blotting analysis revealed that p38IP downregulation enhanced the activity of p38 MAPK and the subsequent accumulation of cyclin-dependent kinase inhibitor p21, thus promoting G1/S arrest and monocyte/macrophage differentiation. Moreover, the decline of GCN5 acetyltransferase caused by p38IP downregulation was required but was not sufficient for monocyte/macrophage differentiation. This study demonstrated a new role for p38IP and a novel miR-200b-3p/p38IP pair in the regulation of monocyte/macrophage differentiation.

The clinical and functional relevance of microparticles induced by activated protein C treatment in sepsis

INTRODUCTION

Activated protein C (APC) induces release of microparticles (MP) from primary physiological cells, which are found in patients undergoing treatment with recombinant human APC (rhAPC) for severe sepsis. We hypothesised that APC on these circulating MPs activate endothelial protease-activated receptor 1 (PAR1) to induce anti-apoptotic and anti-inflammatory properties that can improve patient outcome.

METHODS

This was an experimental study on clinical samples in an intensive care setting, and included patients with severe sepsis who fulfilled criteria for treatment with rhAPC. The number of CD13+ MPs from the patients were analysed to determine their origin. They were also quantified for endothelial protein C receptor (EPCR) and APC expression. Clinical relevance of these MPs were ascertained by comparing survival between the group receiving rhAPC (n = 25) and a control group of untreated patients (n = 25). MPs were also incubated with endothelial cells to analyse apoptotic gene expression, cytoprotection and anti-inflammatory effects.

RESULTS

rhAPC treatment induced a significant increase in circulating MP-associated EPCR by flow cytometry (P < 0.05) and by quantitative ELISA (P < 0.005). APC expression also showed significant increases (P < 0.05). Numerically, CD13+ MPs were higher in rhAPC-treated survivors versus non-survivors. However, the number of non-survivors was low and this was not significantly different. APC on MPs was demonstrated to induce anti-apoptotic and endothelial barrier effects through the activation of endothelial PAR1.

CONCLUSIONS

rhAPC treatment in patients with sepsis significantly increases circulating EPCR + MPs. These MPs were noted to express APC, which has specific anti-apoptotic and anti-inflammatory effects, with a non-significant correlative trend towards survival. This suggests that MPs could disseminate APC function and activate endothelial PAR1 at distal vascular sites.

The human SPT20-containing SAGA complex plays a direct role in the regulation of endoplasmic reticulum stress-induced genes

One of the central questions in eukaryotic transcription is how activators can transmit their signal to stimulate gene expression in the context of chromatin. The multisubunit SAGA coactivator complex has both histone acetyltransferase and deubiquitination activities and remodels chromatin to allow transcription. Whether and how SAGA is able to regulate transcription at specific loci is poorly understood. Using mass spectrometry, immunoprecipitation, and Western blot analysis, we have identified human SPT20 (hSPT20) as the human homologue of the yeast Spt20 and show that hSPT20 is a bona fide subunit of the human SAGA (hSAGA; previously called TFTC/STAGA/PCAF) complex and that hSPT20 is required for the integrity of the hSAGA complex. We demonstrate that hSPT20 and other hSAGA subunits, together with RNA polymerase II, are specifically recruited to genes induced by endoplasmic reticulum (ER) stress. In good agreement with the recruitment of hSAGA to the ER stress-regulated genes, knockdown of hSTP20 hampers ER stress response. Surprisingly, hSPT20 recruitment was not observed for genes induced by another type of stress. These results provide evidence for a direct and specific role of the hSPT20-containing SAGA complex in transcriptional induction of ER stress-responsive genes. Thus, hSAGA regulates the transcription of stress-responsive genes in a stress type-dependent manner.

p38 and a p38-interacting protein are critical for downregulation of E-cadherin during mouse gastrulation

During vertebrate gastrulation, an epithelial to mesenchymal transition (EMT) is necessary for migration of mesoderm from the primitive streak. We demonstrate that p38 MAP kinase and a p38-interacting protein (p38IP) are critically required for downregulation of E-cadherin during gastrulation. In an ENU-mutagenesis screen we identified the droopy eye (drey) mutation, which affects splicing of p38IP. p38IP(drey) mutant embryos display incompletely penetrant defects in neural tube closure, eye development, and gastrulation. A stronger allele (p38IP(RRK)) exhibits gastrulation defects in which mesoderm migration is defective due to deficiency in E-cadherin protein downregulation in the primitive streak. We show that p38IP binds directly to p38 and is required for p38 activation in vivo. Moreover, both p38 and p38IP are required for E-cadherin downregulation during gastrulation. Finally, p38 regulates E-cadherin protein expression downstream from NCK-interacting kinase (NIK) and independently of the regulation of transcription by Fibroblast Growth Factor (Fgf) signaling and Snail.