Human cells are subjected to continuous challenges by different genotoxic stress attacks. DNA damage leads to erroneous mutations, which can alter the function of oncogenes or tumor suppressors, resulting in cancer development. To circumvent this, cells activate the DNA damage response (DDR), which mainly involves cell cycle regulation and DNA repair processes. The tumor suppressor p53 plays a pivotal role in the DDR by halting the cell cycle and facilitating the DNA repair processes. Various pathways and factors participating in the detection and repair of DNA have been described, including scores of RNA-binding proteins (RBPs) and RNAs. It has become increasingly clear that p53’s role is multitasking, and p53 mRNA regulation plays a prominent part in the DDR. This review is aimed at covering the p53 RNA metabolism linked to the DDR and highlights the recent findings.

DNA and RNA binding proteins (DRBPs) are a broad class of molecules that regulate numerous cellular processes across all living organisms, creating intricate dynamic multilevel networks to control nucleotide metabolism and gene expression. These interactions are highly regulated, and dysregulation contributes to the development of a variety of diseases, including cancer. An increasing number of proteins with DNA and/or RNA binding activities have been identified in recent years, and it is important to understand how their activities are related to the molecular mechanisms of cancer. In addition, many of these proteins have overlapping functions, and it is therefore essential to analyze not only the loss of function of individual factors, but also to group abnormalities into specific types of activities in regard to particular cancer types. In this review, we summarize the classes of DNA-binding, RNA-binding, and DRBPs, drawing particular attention to the similarities and differences between these protein classes. We also perform a cross-search analysis of relevant protein databases, together with our own pipeline, to identify DRBPs involved in cancer. We discuss the most common DRBPs and how they are related to specific cancers, reviewing their biochemical, molecular biological, and cellular properties to highlight their functions and potential as targets for treatment.

The two murine double minute (MDM) family members, MDM2 and MDMX, are a well-established negative regulator of p53 activity. Under DNA damage conditions, MDM2 and MDMX are phosphorylated near their RING domains (serine 395 at MDM2 and serine 403 at MDMX) and switch to act as p53 positive regulators. MDMX binds to TP53 mRNA and acts as a chaperone for RNA structure, enabling MDM2 to bind. This interaction enhances TP53 mRNA translation, leading to increased p53 protein production. While the biological significance of this interaction has been described, the specific features of the MDMX–RNA interaction remain poorly understood. We used various MDMX protein constructs to characterize binding to TP53 mRNA and identified that the interaction mediated by the RING domain is modulated by the presence of other domains. Hydrogen-deuterium exchange mass spectrometry (HDX-MS) and binding assays in high salt conditions and various pH demonstrate that the whole protein participates in RNA interaction, with the C-terminal domain likely providing the contact with RNA by electrostatic forces. We show that protein structural changes induced by the chelating agent EDTA or the reducing agent TCEP enhance RNA binding by promoting partial structural destabilization of the protein. Our findings suggest that the MDMX/TP53 mRNA interaction is complex, with the RING domain binding to RNA and being supported by the entire protein, which acts as a scaffold for the RNA interaction. These results contribute to a better understanding of MDMX’s role in TP53 mRNA binding and provide valuable insights for future investigation of the MDM2–MDMX–TP53 mRNA complex, which is crucial for p53 stabilization and activation under DNA-damaging conditions.

The p53 tumor suppressor and the c-Myc oncogene are among the most frequently deregulated genes in human cancers, yet the molecular cross talk between these pathways remains poorly understood. MDM2 is a key negative regulator of p53 and a target for emerging cancer therapies designed to activate p53. Likewise, targeting c-Myc is a long-standing but challenging goal in cancer therapy. Here, we report that the small MDM2-binding drug Milademetan promotes an interaction between MDM2 and the 5’ untranslated region of the c-Myc mRNA, causing a suppression of c-Myc mRNA translation without affecting c-Myc RNA levels. The interaction also occurs under nonproliferative conditions in the absence of drug. Milademetan-mediated c-Myc depletion is accompanied by the induction of apoptosis and suppression of cell proliferation and prevents tumor growth, independently of p53 status. These findings reveal an unexpected mechanism by which MDM2 coordinates two of the most frequently altered pathways in cancer and provide a rationale for targeting c-Myc-driven tumors, including those lacking functional p53, through MDM2 modulators.