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The MDM2 oncoprotein antagonizes the tumor suppressor p53 by physical interaction and ubiquitination. However, it also sustains the progression of DNA replication forks, even in the absence of functional p53. Here, we show that MDM2 binds, inhibits, ubiquitinates, and destabilizes poly(ADP-ribose) polymerase 1 (PARP1). When cellular MDM2 levels are increased, this leads to accelerated progression of DNA replication forks, much like pharmacological inhibition of PARP1. Conversely, overexpressed PARP1 restores normal fork progression despite elevated MDM2. Strikingly, MDM2 profoundly reduces the frequency of fork reversal, revealed as four-way junctions through electron microscopy. Depletion of RECQ1 or the primase/polymerase (PRIMPOL) reverses the MDM2-mediated acceleration of the nascent DNA elongation rate. MDM2 also increases the occurrence of micronuclei, and it exacerbates camptothecin-induced cell death. In conclusion, high MDM2 levels phenocopy PARP inhibition in modulation of fork restart, representing a potential vulnerability of cancer cells.
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http://dx.doi.org/10.1016/j.celrep.2022.110879 | DOI Listing |
mSphere
September 2025
Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Blacksburg, Virginia, USA.
Apicomplexan AP2 (ApiAP2) family proteins are a family of transcription factors that are known to regulate gene expression in apicomplexan pathogens, including . In this study, we focused on TgAP2X-7, a member of the APiAP2 family that is predicted to be essential for fitness. Endogenous tagging of TgAP2X-7 followed by immunofluorescence analysis revealed that it's a cell cycle-regulated nuclear protein with peak expression in the G1 phase.
View Article and Find Full Text PDFElife
September 2025
Graduate School of Life Science, Hokkaido University, Sapporo, Japan.
DNA replication requires recruitment of Cdc45 and GINS into the MCM double hexamer by initiation factors to form an active helicase, the Cdc45-MCM-GINS (CMG) complex, at the replication origins. The initiation factor Sld3 is a central regulator of Cdc45 and GINS recruitment, working with Sld7 together. However, the mechanism through which Sld3 regulates CMG complex formation remains unclear.
View Article and Find Full Text PDFMicrobiol Spectr
September 2025
Department of Viral Transformation, Leibniz Institute of Virology (LIV), Martinistraße, Hamburg, Germany.
Unlabelled: Human adenoviruses (HAdVs) induce significant reorganization of the nuclear environment, leading to the formation of virus-induced subnuclear structures known as replication compartments (RCs). Within these RCs, viral genome replication, gene expression, and modulation of cellular antiviral responses are tightly coordinated, making them valuable models for studying virus-host interactions. In a recent study, we analyzed the protein composition of HAdV type 5 (HAdV-C5) RCs isolated from infected primary cells at different time points during infection using quantitative proteomics.
View Article and Find Full Text PDFJ Virol
September 2025
Laboratory of Virology, Wageningen University & Research, Wageningen, the Netherlands.
Vertebrate animals and many small DNA and single-stranded RNA viruses that infect vertebrates have evolved to suppress genomic CpG dinucleotides. All organisms and most viruses additionally suppress UpA dinucleotides in protein-coding RNA. Synonymously recoding viral genomes to introduce CpG or UpA dinucleotides has emerged as an approach for viral attenuation and vaccine development.
View Article and Find Full Text PDFFront Microbiol
August 2025
Institute of Infectious Diseases, Guangzhou Eighth People's Hospital, Guangzhou Medical University, Guangzhou, Guangdong, China.
Introduction: Low-level viremia (LLV) in HIV infection, defined as detectable but low plasma viral load, is associated with an increased risk of virological failure (VF); however, the mechanisms underlying LLV remain unclear. Monocytes, as potential viral reservoirs, can migrate into tissues and differentiate into tissue-resident macrophage reservoirs, playing a critical role in viral dissemination and potentially driving persistent viremia.
Methods: This study aimed to analyze and compare the molecular characteristics of near-full-length HIV-1 proviral DNA quasispecies from monocytes in three distinct virological response groups: VF, LLV, and virological suppression (VS).