The MDM2 oncoprotein is a cellular inhibitor of the p53 tumor suppressor in that it can bind the transactivation domain of p53 and downregulate its ability to activate transcription. In certain cancers, MDM2 amplification is a common event and contributes to the inactivation of p53. The crystal structure of the 109-residue amino-terminal domain of MDM2 bound to a 15-residue transactivation domain peptide of p53 revealed that MDM2 has a deep hydrophobic cleft on which the p53 peptide binds as an amphipathic alpha helix. The interface relies on the steric complementarity between the MDM2 cleft and the hydrophobic face of the p53 alpha helix and, in particular, on a triad of p53 amino acids-Phe19, Trp23, and Leu26-which insert deep into the MDM2 cleft. These same p53 residues are also involved in transactivation, supporting the hypothesis that MDM2 inactivates p53 by concealing its transactivation domain. The structure also suggests that the amphipathic alpha helix may be a common structural motif in the binding of a diverse family of transactivation factors to the TATA-binding protein-associated factors.

The 90-kDa cellular protein encoded by the mouse mdm-2 oncogene binds to the p53 protein in vivo and inhibits its transactivation function (J. Momand, G. P. Zambetti, D. C. Olson, D. George, and A. J. Levine, Cell 69:1237-1245

SARS-CoV-2 is the etiological agent of COVID-19. Most of SARS-CoV-2 carriers are assumed to exhibit no or mild non-specific symptoms. Thus, they may contribute to the rapid and mostly silent circulation of the virus among humans. Since SARS-CoV-2 can be detected in stool samples it has recently been proposed to monitor SARS-CoV-2 in wastewaters (WW) as a complementary tool to investigate virus circulation in human populations. In the present work we assumed that the quantification of SARS-CoV-2 genomes in wastewaters should correlate with the number of symptomatic or non-symptomatic carriers. To test this hypothesis, we performed a time-course quantitative analysis of SARS-CoV-2 by RT-qPCR in raw wastewater samples collected from several major wastewater treatment plant (WWTP) of the Parisian area. The study was conducted from March 5 to April 23 2020, therefore including the lockdown period in France (since March 17 2020). We confirmed that the increase of genome units in raw wastewaters accurately followed the increase of human COVID-19 cases observed at the regional level. Of note, the viral genomes could be detected before the beginning of the exponential growth of the epidemic. As importantly, a marked decrease in the quantities of genomes units was observed concomitantly with the reduction in the number of new COVID-19 cases which was an expected consequence of the lockdown. As a conclusion, this work suggests that a quantitative monitoring of SARS-CoV-2 genomes in wastewaters should bring important and additional information for an improved survey of SARS-CoV-2 circulation at the local or regional scale.

Throughout the purification of the mdm-2 or mdm-2-p53 protein complexes, a protein with a molecular weight of 34,000 was observed to copurify with these proteins. Several monoclonal antibodies directed against distinct epitopes in the mdm-2 or p53 protein coimmunoprecipitated this 34,000-molecular-weight protein, which did not react to p53 or mdm-2 polyclonal antisera in a Western immunoblot. The N-terminal amino acid sequence of this 34,000-molecular-weight protein demonstrated that the first 40 amino acids were identical to the ribosomal L5 protein, found in the large rRNA subunit and bound to 5S RNA. Partial peptide maps of the authentic L5 protein and the 34,000-molecular-weight protein were identical. mdm-2-L5 and mdm-2-L5-p53 complexes were shown to bind 5S RNA specifically, presumably through the known specificity of L5 protein for 5S RNA. In 5S RNA-L5-mdm-2-p53 ribonucleoprotein complexes, it was also possible to detect the 5.8S RNA which has been suggested to be covalently linked to a percentage of the p53 protein in a cell. These experiments have identified a unique ribonucleoprotein complex composed of 5S RNA, L5 protein, mdm-2 proteins, p53 protein, and possibly the 5.8S RNA. While the function of such a ribonucleoprotein complex is not yet clear, the identity of its component parts suggests a role for these proteins and RNA species in ribosomal biogenesis, ribosomal transport from the nucleus to the cytoplasm, or translational regulation in the cell.The mdm-2 gene was originally detected as an amplified DNA sequence on double minute chromosomes in the 3T3DM cell line, which was derived from spontaneously transformed BALB/c 3T3 cells (1). Subsequently, it was shown that overexpression of the mdm-2 gene can increase the tumorigenic potential of cells (5), thus qualifying it as an oncogene. Indeed, the mdm-2 oncogene is amplified in a variety of osteogenic sarcomas and soft tissue sarcomas of humans (4, 14). The mdm-2 gene encodes several proteins with molecular weights that vary between 90,000 and 57,000 (15), and these proteins express distinct epitopes on different mdm-2 proteins, as characterized by using a variety of mdm-2-specific monoclonal antibodies (2).The only known function of these mdm-2 proteins is that some subset of them bind to the p53 protein and block its ability to act as a transcription factor (12). Amino acid residues 19 to 102 from the mdm-2 protein (of a total of 491) and amino acid residues 1 to 52 of the p53 protein (of a total of 393) are required to form p53-mdm-2 complexes (2), so the N termini of both proteins make these protein contacts. The N-terminal 42 amino acids of p53 constitute the transactivation domain of p53 (6, 17), which presumably makes contact with the transcriptional machinery of the cell (20), resulting in enhanced mRNA synthesis. Indeed, the same two amino acids (Leu-22 and Trp-23) required for transcriptional activation in the N terminus of the p53 protein have also been shown to be critical for mdm-2 binding to the p53 protein (9).Several forms of the m...

No abstract

The Mdm2 gene is overexpressed in several human tumors. The oncogenic potential of Mdm2 is partially explained by the inhibition of the activity of the tumor suppressor protein p53. Determination of the threedimensional structure of complexes between Mdm2 and the N-terminal p53 peptide provided a molecular basis for the inhibition of the transcriptional function of p53 by Mdm2. More dramatically, p53 is targeted by Mdm2 for rapid degradation. The Mdm2 gene itself is activated by p53, which gives the opportunity for feed-back control of p53 activity. Keeping p53 under control is most likely the major task of Mdm2 during early development. Recently, evidence was provided for an alternative, p53-independent function of Mdm2.

Introduction Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the etiological agent of coronavirus disease (COVID-19). People infected with SARS-CoV-2 may exhibit no or mild non-specific symptoms; thus, they may contribute to silent circulation of the virus among humans. Since SARS-CoV-2 RNA can be detected in stool samples, monitoring SARS-CoV-2 RNA in waste water (WW) has been proposed as a complementary tool to investigate virus circulation in human populations. Aim To test if the quantification of SARS-CoV-2 genomes in WW correlates with the number of symptomatic or non-symptomatic carriers. Method We performed a time-course quantitative analysis of SARS-CoV-2 by RT-qPCR in raw WW samples collected from several major WW treatment plants in Greater Paris. The study period was 5 March to 23 April 2020, including the lockdown period in France (from 17 March). Results We showed that the increase of genome units in raw WW accurately followed the increase of human COVID-19 cases observed at the regional level. Of note, the viral genome could be detected before the epidemic grew massively (around 8 March). Equally importantly, a marked decrease in the quantities of genome units was observed concomitantly with the reduction in the number of new COVID-19 cases, 29 days following the lockdown. Conclusion This work suggests that a quantitative monitoring of SARS-CoV-2 genomes in WW could generate important additional information for improved monitoring of SARS-CoV-2 circulation at local or regional levels and emphasises the role of WW-based epidemiology.

The mdm2 oncogene encodes a 90-kDa protein that can bind to the p53 tumor suppressor protein and negatively regulate its functions in transcription, cell cycle arrest, and apoptosis. The mdm2 gene is frequently amplified in human sarcomas, which may be responsible for the malignant transformations. We present evidence that the mdm2 oncoprotein is cleaved by an interleukin 1␤-converting enzyme-like protease (caspase) during p53-mediated apoptosis. The protease that cleaves mdm2 has a specificity similar to that of CPP32 (caspase-3), and recombinant caspase-3 is able to cleave mdm2 in vitro. The protease cleavage site has been mapped to between residue 361 and 362 of human mdm2. The proteolytic cleavage removes the COOH-terminal RING finger domain of mdm2, resulting in the loss of RNA binding activity. The p53 binding and inhibition functions of mdm2 are not affected by the cleavage. The cleavage site sequence of mdm2 is evolutionarily conserved, suggesting that regulation by caspase cleavage during apoptosis is an important feature of mdm2.