Biology subjects

Spektor, A.

Publications and source records attributed to Spektor, A..

6 recordsLinked to original sources

bioRxiv2026

The TIRR–53BP1 axis controls PLK1 spatiotemporal regulation during mitosis

p53-binding protein 1 (53BP1) is a key mediator of the DNA damage response and genome stability. While its interphase function is well-characterized, its mitotic role remains less understood. Here we show that aberrant activation of 53BP1 through the loss of its negative regulator, TIRR, leads to mitotic abnormalities including altered spindle geometry, kinetochore-microtubule (k-MT) attachment errors and whole chromosome missegregation. We demonstrate that loss of TIRR results in excess interaction between 53BP1 and the key mitotic kinase Polo-like kinase 1 (PLK1), altering PLK1s activation, spatial distribution, and its interaction with known PLK1 substrates at multiple mitotic stages. Moreover, due to PLK1s established role in CENP-A loading, hyperactivation of 53BP1 compromises CENP-A loading, triggers gradual loss of CENP-A from centromeres and generates severe kinetochore assembly defects. These findings uncover a non-canonical mitotic function of 53BP1 as a key regulator of PLK1 activity and chromosome segregation fidelity.

Cell Biology↗

bioRxiv2025

Ionizing Radiation Shapes Genome Evolution Through Nuclear Abnormalities That Trigger Delayed Proliferative Death

Ionizing radiation (IR) is widely used in cancer therapy, yet the mechanisms by which IR-induced DNA damage translates into delayed proliferative death and secondary malignancy risk remain incompletely defined. Radiation generates double-strand breaks (DSBs) that are frequently misrepaired, giving rise to micronuclei and chromosome bridges--abnormal nuclear structures known to drive chromosomal instability. Here, a modified live-cell imaging and single-cell whole-genome sequencing (WGS) approach was used to directly connect early cytological responses to genome-wide outcomes in cells exposed to graded IR doses. Tracking asynchronously cycling cells revealed that micronuclei, chromosome bridges, and nuclear fragmentation form at high frequency during the first mitosis after irradiation, in a strongly cell-cycle-dependent manner: micronuclei were most frequent after S-phase irradiation, whereas chromosome bridges predominated when damage occurred in G1 or S phase. Lineage tracing combined with clonogenic assays showed that formation of abnormal nuclear structures in the first post-irradiation division is a major determinant of long-term proliferative capacity, with centromere-containing (centric) fragments and bridges exerting a stronger anti-proliferative effect than acentric micronuclei. Single-cell WGS of daughter and granddaughter cells demonstrated that these structures generate reciprocal copy-number changes, clustered rearrangements, and chromothripsis-like events that are largely incompatible with sustained proliferation. In contrast, bulk WGS of surviving single-cell-derived clones revealed only modest increases in single-nucleotide variants and indels but an enrichment of nonhomologous end-joining-associated deletion signatures and selected structural variants, including amplification of a pre-existing 12p gain. These findings identify abnormal nuclear structures as key intermediates linking IR-induced DNA lesions to mitotic catastrophe and provide insight into selective tolerance of specific rearrangements.

cell biology↗

bioRxiv2025

Synergistic targeting of MCL1 and caspases for enhanced anti-tumor immunity in breast cancer.

Breast cancer remains largely unresponsive to immunotherapy due to its immunologically "cold" nature, marked by low cytolytic activity and a paucity of neoantigens. To overcome this, we developed a novel therapeutic approach to activate the cGAS-STING pathway, a critical mediator of the type I interferon response essential for effective anti-tumor immunity. We demonstrate that combined inhibition of MCL1 and caspases robustly triggers a type I IFN response in breast cancer cells, effectively remodeling the tumor microenvironment by increasing immune cell infiltration and enhancing antigen presentation. In immunocompetent syngeneic mouse models, this combination therapy significantly suppressed tumor growth, an effect that was reversed upon blockade of the IFN signaling axis. Mechanistically, our findings reveal that co-targeting MCL1 and caspases reprograms the tumor microenvironment enhancing immune surveillance. Given the established safety profiles of both drug classes, this strategy offers a promising and rapidly deployable approach to sensitize breast tumors to immunotherapy.

cancer biology↗

bioRxiv2025

Human CDK5-cyclin B1 structures uncover a conserved mitotic CDK activation mechanism

Cyclin-dependent kinase 5 (CDK5), long considered atypical and activated by non-cyclin cofactors in neurons, also functions in mitosis. To resolve its activation mechanism during mitosis, we determined the first high-resolution crystal structures of CDK5-cyclin B1 in apo and nucleotide-bound states. Contrary to AlphaFold predictions, we find CDK5 structures unexpectedly mirrors CDK1-cyclin B1 assembly and activation, establishing CDK5 as a bona fide mitotic kinase acting in parallel with CDK1.

biochemistry↗

bioRxiv2023

2D and 3D multiplexed subcellular profiling of nuclear instability in human cancer

Nuclear atypia, including altered nuclear size, contour, and chromatin organization, is ubiquitous in cancer cells. Atypical primary nuclei and micronuclei can rupture during interphase; however, the frequency, causes, and consequences of nuclear rupture are unknown in most cancers. We demonstrate that nuclear envelope rupture is surprisingly common in many human cancers, particularly glioblastoma. Using highly-multiplexed 2D and super-resolution 3D-imaging of glioblastoma tissues and patient-derived xenografts and cells, we link primary nuclear rupture with reduced lamin A/C and micronuclear rupture with reduced lamin B1. Moreover, ruptured glioblastoma cells activate cGAS-STING-signaling involved in innate immunity. We observe that local patterning of cell states influences tumor spatial organization and is linked to both lamin expression and rupture frequency, with neural-progenitor-cell-like states exhibiting the lowest lamin A/C levels and greatest susceptibility to primary nuclear rupture. Our study reveals that nuclear instability is a core feature of cancer, and links nuclear integrity, cell state, and immune signaling.

cancer biology↗

bioRxiv2019

Mechanisms Generating Cancer Genome Complexity From A Single Cell Division Error

The chromosome breakage-fusion-bridge (BFB) cycle is a mutational process that produces gene amplification and genome instability. Signatures of BFB cycles can be observed in cancer genomes with chromothripsis, another catastrophic mutational process. Here, we explain this association by identifying a mutational cascade downstream of chromosome bridge formation that generates increasing amounts of chromothripsis. We uncover a new role for actomyosin forces in bridge breakage and mutagenesis. Chromothripsis then accumulates starting with aberrant interphase replication of bridge DNA, followed by an unexpected burst of mitotic DNA replication, generating extensive DNA damage. Bridge formation also disrupts the centromeric epigenetic mark, leading to micronucleus formation that itself promotes chromothripsis. We show that this mutational cascade generates the continuing evolution and sub-clonal heterogeneity characteristic of many human cancers.

cancer biology↗