Vincent Maréchal

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, 1992). cDNA clones encoding the human homolog of the mdm-2 protein (also called hdm-2) were isolated from a HeLa cell cDNA library. A series of monoclonal antibodies have been generated against human mdm-2 protein, and the epitopes recognized by these antibodies have been mapped. By construction of a series of deletion mutants, the region of the mdm-2 protein that is critical for complex formation with the p53 protein has been mapped to the N-terminal portion of the human mdm-2 protein. Interestingly, a monoclonal antibody with an epitope located in this same region failed to immunoprecipitate the mdm-2-p53 complex and appeared to recognize only free mdm-2 protein. The domain of the p53 protein that is sufficient for interaction with human mdm-2 protein has been mapped to the N-terminal 52 amino acid residues of the p53 protein. This region contains the transactivation domain of p53, suggesting that mdm-2 may inhibit p53 function by disrupting its interaction with the general transcription machinery.

Genetic alterations in the p53 and mdm2 genes have been reported to occur in soft tissue sarcomas. This study was designed to determine the prevalence and potential clinical value of detected molecular abnormalities and altered patterns of expression of mdm2 and p53 genes in adult soft tissue sarcomas. A cohort of 211 soft tissue sarcomas from adults that were both clinically and pathologically well characterized was analyzed. Monoclonal antibodies directed against mdm2 and p53 proteins were used to measure overexpression of these proteins in the nuclei of cells from sections of these tumors. Seventy-six of 207 tumors had abnormally high levels of mdm2 proteins and 56 of 211 tumors overexpressed p53 protein. Twenty-two cases had abnormally high levels of both mdm2 and p53 proteins based upon immunoreactivity with these antibodies. There was a striking statistically significant correlation between the overexpression of p53 and mdm2 proteins in the same tumor and poor survival (P < 0.05) of the patients. A group of 73 soft tissue sarcomas was chosen for analysis using Southern blots, single strand conformation polymorphisms, and direct DNA sequencing to confirm mdm2 gene amplifications and p53 mutations and correlate these with the results of the immunoreactivities. The overexpression of p53 and mdm2 proteins in the nuclei of tumor cells did not always correlate well with gene amplification at the mdm2 locus or mutation at the p53 gene. The possible reasons for these discrepancies are discussed.

IntroductionSevere 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.AimTo test if the quantification of SARS-CoV-2 genomes in WW correlates with the number of symptomatic or non-symptomatic carriers.MethodWe 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).ResultsWe 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.ConclusionThis 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.

Summary 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 5 March to 23 April 2020, therefore including the lockdown period in France (since 17 March 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. A s 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.