Biology subjects

Meitinger, F.

Publications and source records attributed to Meitinger, F..

6 recordsLinked to original sources

bioRxiv2025

The mitotic stopwatch synergizes with mild p53 activation to halt cell proliferation

The mitotic stopwatch suppresses proliferation of cell lineages experiencing prolonged mitosis that are prone to chromosome missegregation and tumorigenesis. It converts extended mitotic duration into heritable USP28-53BP1 complexes that stabilize p53 and accumulate over generations. To identify genes whose knockout activates the stopwatch, we performed a CRISPR/Cas9 screen comparing dropout kinetics of essential-gene gRNAs in cells lacking versus possessing the stopwatch. Two classes of knockouts emerged: one (27/60 top hits) that prolonged mitosis, and another (33/60 top hits) that mildly elevated p53 without significant mitotic defects, indicating that the stopwatch synergizes with mild p53 activation to halt proliferation. Mild p53 elevation lowered the stopwatch complex threshold for daughter cell arrest and slightly prolonged mitosis. Integrated over successive divisions, the cumulative effect of multiple short mitotic extensions triggered stopwatch-dependent arrest. Thus, the mitotic stopwatch endows the p53 network with a durable lineage memory of modest stress, explaining its tumor-suppressive role.

cell biology↗

bioRxiv2025

Cancer-Associated USP28 Missense Mutations Disrupt 53BP1 Interaction and p53 Stabilization

Cellular stress response pathways are essential for genome stability and are frequently dysregulated in cancer. Following mitotic stress, the ubiquitin-specific protease 28 (USP28) and the p53-binding protein 1 (53BP1) form a stable, heritable complex to stabilize the tumor suppressor p53, triggering cell cycle arrest or apoptosis. Here we determine the mechanism by which USP28 stabilizes p53 and show that USP28 is required not only for an efficient stress response but also for maintaining basal p53 levels in some cancer cells. Loss of functional USP28 allows cells to evade mitotic stress and DNA damage responses in a manner that is specific to cell type and cancer context. We identify a prevalent, shorter USP28 isoform critical for p53 stabilization. Its C-terminal domain mediates PLK1-dependent binding to 53BP1, a dimerization-driven interaction necessary for mitotic stress memory, p53 stabilization, and cell cycle arrest. Cancer-associated missense mutations in this domain disrupt 53BP1 binding, impair nuclear localization, and destabilize USP28, compromising p53 stabilization. Notably, mutations in the 53BP1-binding domain occur more frequently in tumors than those in the catalytic domain, suggesting a potential role in cancer progression and implications for therapeutic strategies.

cell biology↗

bioRxiv2024

TRIM37 employs peptide motif recognition and substrate-dependent oligomerization to prevent ectopic spindle pole assembly

Tightly controlled duplication of centrosomes, the major microtubule-organizing centers of animal cells, ensures bipolarity of the mitotic spindle and accurate chromosome segregation. The RBCC (RING-B-box-coiled coil) ubiquitin ligase TRIM37, whose loss is associated with elevated chromosome missegregation and the tumor-prone developmental human disorder Mulibrey nanism, prevents the formation of ectopic spindle poles that assemble around structured condensates containing the centrosomal protein centrobin. Here, we show that TRIM37s TRAF domain, unique in the extended TRIM family, engages peptide motifs in centrobin to suppress condensate formation. TRIM proteins form anti-parallel coiled-coil dimers with RING-B-box domains on each end. Oligomerization due to RING-RING interactions and conformational regulation by B-box-2-B-box-2 interfaces are critical for TRIM37 to suppress centrobin condensate formation. These results indicate that, analogous to anti-viral TRIM ligases, TRIM37 activation is linked to the detection of oligomerized substrates. Thus, TRIM37 couples peptide motif recognition and substrate-dependent oligomerization to effect ubiquitination-mediated clearance of ectopic centrosomal protein assemblies.

cell biology↗

bioRxiv2022

Control of cell proliferation by memories of mitosis

Mitotic duration is tightly constrained, with extended mitotic duration being a characteristic of potentially problematic cells prone to chromosome missegregation and genomic instability. We show that memories of mitotic duration are integrated by a p53-based mitotic stopwatch pathway to exert tight control over proliferation. The stopwatch halts proliferation of the products of a single significantly extended mitosis or of successive modestly extended mitoses. Time in mitosis is monitored via mitotic kinase-regulated assembly of stopwatch complexes that are transmitted to daughter cells. The stopwatch is inactivated in p53-mutant cancers, as well as in a significant proportion of p53-wildtype cancers, consistent with classification of stopwatch complex subunits as tumor suppressors. Stopwatch status additionally influences efficacy of anti-mitotic agents currently used or in development for cancer therapy. One-Sentence SummaryTime spent in mitosis is carefully monitored to halt the proliferation of potentially dangerous cells in a population.

cancer biology↗

bioRxiv2020

CTCF Promotes Long-range Enhancer-promoter Interactions and Lineage-specific Gene Expression in Mammalian Cells

Topologically associating domains (TAD) and insulated neighborhoods (INs) have been proposed to constrain enhancer-promoter communications to enable cell-type specific transcription programs, but recent studies show that disruption of TADs and INs resulted in relatively mild changes in gene expression profiles. To better understand the role of chromatin architecture in dynamic enhancer-promoter contacts and lineage-specific gene expression, we have utilized the auxin-inducible degron system to acutely deplete CTCF, a key factor involved in TADs and IN formation, in mouse embryonic stem cells (mESCs) and examined chromatin architecture and gene regulation during neural differentiation. We find that while CTCF depletion leads to global weakening of TAD boundaries and loss of INs, only a minor fraction of enhancer-promoter contacts are lost, affecting a small subset of genes. The CTCF-dependent enhancer-promoter contacts tend to be long-range, spanning hundreds of kilobases, and are established directly by CTCF binding to promoters. Disruption of CTCF binding at the promoter reduces enhancer-promoter contacts and transcription, while artificial tethering of CTCF to the promoter restores the enhancer-promoter contacts and gene activation. Genome-wide analysis of CTCF binding and gene expression across multiple mouse tissues suggests that CTCF-dependent promoter-enhancer contacts may regulate expression of additional mouse genes, particularly those expressed in the brain. Our results uncover both CTCF-dependent and independent enhancer-promoter contacts, and highlight a distinct role for CTCF in promoting enhancer-promoter contacts and gene activation in addition to its insulator function.

genomics↗

bioRxiv2017

Preservation of Chromatin Organization after Acute Loss of CTCF in Mouse Embryonic Stem Cells

The CCCTC-binding factor (CTCF) is widely regarded as a key player in chromosome organization in mammalian cells, yet direct assessment of the impact of loss of CTCF on genome architecture has been difficult due to its essential role in cell proliferation and early embryogenesis. Here, using auxin-inducible degron techniques to acutely deplete CTCF in mouse embryonic stem cells, we show that cell growth is severely slowed yet chromatin organization remains largely intact after loss of CTCF. Depletion of CTCF reduces interactions between chromatin loop anchors, diminishes occupancy of cohesin complex genome-wide, and slightly weakens topologically associating domain (TAD) structure, but the active and inactive chromatin compartments are maintained and the vast majority of TAD boundaries persist. Furthermore, transcriptional regulation and histone marks associated with enhancers are broadly unchanged upon CTCF depletion. Our results suggest CTCF-independent mechanisms in maintenance of chromatin organization.

genomics↗