Mutations in the p53 gene are most frequent in cancer. Many p53 mutants possess transforming activity in vitro. In cells transformed by such mutants, the mutant protein is oligomerized with endogenous cell p53. To determine the relevance of oligomerization for transformation, miniproteins containing C-terminal portions of p53 were generated. These miniproteins, although carrying no point mutation, transformed at least as efficiently as full-length mutant p53. Transforming activity was coupled with the ability to oligomerize with wild-type p53, as well as with the ability to abrogate sequence-specific DNA binding by coexpressed wild-type p53. These findings suggest that p53-mediated transformation may operate through a dominant negative mechanism, involving the generation of DNA binding-incompetent oligomers.

The mdm2 gene is a target for transcriptional activation by the p53 tumor suppressor gene product. Previous work has revealed that the mouse mdm2 gene contains two promoters: one is located upstream to the gene and is active in the absence of p53, the other resides within the first intron and requires p53 for transcriptional activity. To determine whether this unique promoter activation pattern is biologically important, we investigated the structure and function of the corresponding region of the human mdm2 (hmdm2) gene. We report here that the hmdm2 gene also contains an intronic, p53-dependent promoter. The structural features of this promoter are highly conserved between mouse and man, as opposed to the lack of conservation of the first exon. This promoter is triggered in vivo in the presence of activated wild type p53, leading to the production of novel mRNA species. The intronic hmdm2 promoter contains two tandem p53 binding elements. Deletion analysis suggests that optimal promoter activity requires the simultaneous binding of p53 to both elements; this may serve to prevent premature triggering of the promoter by p53.

The novel highly transmissible human coronavirus SARS-CoV-2 is the causative agent of the COVID-19 pandemic. Thus far, there is no approved therapeutic drug specifically targeting this emerging virus. Here we report the isolation and characterization of a panel of human neutralizing monoclonal antibodies targeting the SARS-CoV-2 receptor binding domain (RBD). These antibodies were selected from a phage display library constructed using peripheral circulatory lymphocytes collected from patients at the acute phase of the disease. These neutralizing antibodies are shown to recognize distinct epitopes on the viral spike RBD. A subset of the antibodies exert their inhibitory activity by abrogating binding of the RBD to the human ACE2 receptor. The human monoclonal antibodies described here represent a promising basis for the design of efficient combined post-exposure therapy for SARS-CoV-2 infection.

An immune selection procedure was employed in order to isolate p53 binding sites from mouse genomic DNA. Two DNA clones capable of tight specific interaction with wild type p53 were subjected to further characterization. In both cases, the p53 binding regions displayed a high degree of sequence homology with the consensus binding site defined for human genomic DNA. One of the clones was found to be derived from the LTR of a retrovirus‐like element (a member of the GLN family). The region encompassing the GLN LTR p53 binding site could confer p53 responsiveness upon a heterologous promoter. Furthermore, the expression of the endogenous, chromosomally integrated GLN elements was significantly induced upon activation of wild type p53 in cells harboring a temperature sensitive p53 mutant. Finally, it was demonstrated that p53 ‐ MDM2 complexes fail to bind tightly to such a p53 binding site. This may contribute to the inhibition by MDM2 of p53‐mediated transcriptional activation.

No abstract