MDM4/HIPK2/p53 cytoplasmic assembly uncovers coordinated repression of molecules with anti-apoptotic activity during early DNA damage response.

The p53 inhibitor, MDM4 (MDMX) is a cytoplasmic protein with p53-activating function under DNA damage conditions. Particularly, MDM4 promotes phosphorylation of p53 at Ser46, a modification that precedes different p53 activities. We investigated the mechanism by which MDM4 promotes this p53 modification and its consequences in untransformed mammary epithelial cells and tissues. In response to severe DNA damage, MDM4 stimulates p53Ser46(P) by binding and stabilizing serine-threonine kinase HIPK2. Under these conditions, the p53-inhibitory complex, MDM4/MDM2, dissociates and this allows MDM4 to promote p53/HIPK2 functional interaction. Comparative proteomic analysis of DNA damage-treated cells versus -untreated cells evidenced a diffuse downregulation of proteins with anti-apoptotic activity, some of which were targets of p53Ser46(P)/HIPK2 repressive activity. Importantly, MDM4 depletion abolishes the downregulation of these proteins indicating the requirement of MDM4 to promote p53-mediated transcriptional repression. Consistently, MDM4-mediated HIPK2/p53 activation precedes HIPK2/p53 nuclear translocation and activity. Noteworthy, repression of these proteins was evident also in mammary glands of mice subjected to γ-irradiation and was significantly enhanced in transgenic mice overexpressing MDM4. This study evidences the flexibility of MDM2/MDM4 heterodimer, which allows the development of a positive activity of cytoplasmic MDM4 towards p53-mediated transcriptional function. Noteworthy, this activity uncovers coordinated repression of molecules with shared anti-apoptotic function which precedes active cell apoptosis and that are frequently overexpressed and/or markers of tumour phenotype in human cancer.

Che-1 modulates the decision between cell cycle arrest and apoptosis by its binding to p53.

The tumor suppressor p53 is mainly involved in the transcriptional regulation of a large number of growth-arrest- and apoptosis-related genes. However, a clear understanding of which factor/s influences the choice between these two opposing p53-dependent outcomes remains largely elusive. We have previously described that in response to DNA damage, the RNA polymerase II-binding protein Che-1/AATF transcriptionally activates p53. Here, we show that Che-1 binds directly to p53. This interaction essentially occurs in the first hours of DNA damage, whereas it is lost when cells undergo apoptosis in response to posttranscriptional modifications. Moreover, Che-1 sits in a ternary complex with p53 and the oncosuppressor Brca1. Accordingly, our analysis of genome-wide chromatin occupancy by p53 revealed that p53/Che1 interaction results in preferential transactivation of growth arrest p53 target genes over its pro-apoptotic target genes. Notably, exposure of Che-1(+/-) mice to ionizing radiations resulted in enhanced apoptosis of thymocytes, compared with WT mice. These results confirm Che-1 as an important regulator of p53 activity and suggest Che-1 to be a promising yet attractive drug target for cancer therapy.

[Italian consensus on Eular 2003 recommendations for the treatment of knee osteoarthritis]. / Consensus italiana sulle raccomandazioni dell'EULAR 2003 per il trattamento dell'artrosi del ginocchio.

The recommendations for the management of osteoarthritis (OA) of the knee firstly proposed by the EULAR in 2000, have been updated in 2003. One of the most important objectives of the expert charged to provide these recommendations was their dissemination. Thus, the information generated may be used by each individual country to produce their own set of management guidelines and algorithms for treatment in primary care. The Italian Society of Rheumatology (SIR) and the Italian League against Rheumatism (LIMAR) have organised a Consensus on the EULAR recommendations 2003 with the aim to analyse their acceptability and applicability according to our own experience and local situations in the Italy. The results of this Consensus have demonstrated that a large majority of the EULAR recommendations are endorsed by the Italian experts. Furthermore, the final document of the Italian Consensus clearly indicated the need that specialists involved in the management of knee OA strongly encourage the dissemination of the EULAR 2003 recommendations also in Italy.

[Magnetic resonance imaging of the knee. Preliminary study of non-neoplastic osteoarticular pathology]. / La RM del ginocchio. Studio preliminare della patologia osteo-articolare non neoplastica.

Magnetic Resonance Imaging (MRI) has been applied to musculoskeletal pathoanatomy and has proved to be useful in the detection and characterization of knee pathology. Thirty-two acutely injured knees and 8 normal knees were examined. The images were obtained in the Diagnostic Centre RMRC of Naples on a 0.5 T superconductive magnet system, using a surface coil and a spin-echo pulse sequence (SE 600/28 ms). The examined limb was immobilized and bent at 8-10 degrees, extrarotated for the examination of the anterior cruciate ligament (ACL) only. Images were obtained on a 256 x 256 matrix and had a 2 or 4-mm thickness. MRI clearly showed all the anatomical structures. The anterior and posterior cruciate ligaments (ACL and PCL) and the patellar ligament were shown by sagittal SE images through the intercondylar notch; the tibial and fibular collateral ligaments (TCL and FCL) were evaluated on coronal SE images; the articular capsula and menisci on axial transverse SE images. Objective criteria for ACL and PCL tears were: lack of continuity of the signal and change in signal intensity; in meniscal pathology, menisci with small linear regions of increased signal or with grossly truncated shape were interpreted as tears. Preliminary results of this study indicate that MRI together with clinical evaluation may be an useful non-invasive procedure in the assessment of acute injuries of the knee.