Biology subjects

Lototska, L.

Publications and source records attributed to Lototska, L..

3 recordsLinked to original sources

bioRxiv2025

DDIAS is a single-stranded DNA-binding effector of the TOPBP1-CIP2A complex in mitosis

DNA double-strand breaks and unresolved DNA replication intermediates are particularly dangerous during mitosis. Paradoxically, cells inactivate canonical DNA repair mechanisms during chromosome segregation in favor of alternative pathways that depend on TOPBP1 and CIP2A, but how they function is still poorly defined. Here, we describe the identification of DDIAS as a mitosis-specific DNA damage response protein. We establish DDIAS as a phosphorylation-dependent component and effector of the TOPBP1-CIP2A complex with single-stranded DNA (ssDNA)-binding activity, and thereby delineate a ssDNA protection mechanism that safeguards chromosome integrity during mitosis, particularly in BRCA-deficient cells. We also identify biallelic inactivating mutations in DDIAS in a patient with a severe neurodevelopmental disorder. These findings highlight for the first time a potential physiological role for the DNA damage response in mitosis.

molecular biology↗

bioRxiv2024

TelAP2 links TelAP1 to the telomere complex in Trypanosoma brucei

The extracellular parasite Trypanosoma brucei evades the immune system of the mammalian host by periodically exchanging its variant surface glycoprotein (VSG) coat. Hereby, only one VSG gene is transcribed from one of 15 subtelomeric so-called bloodstream form expression sites (BES) at any given timepoint, while all other BESs are silenced. VSG gene expression is altered by homologous recombination using a large VSG gene repertoire or by a so-called in situ switch, which activates a previously silent BES. Transcriptional activation, VSG switching and VSG silencing during developmental differentiation from the bloodstream form to the procyclic form present in the tsetse fly vector are tightly regulated. Due to their subtelomeric position, telomere-associated proteins are involved in the regulation of VSG expression. Three functional homologs of mammalian telomere complex proteins have been characterized thus far, and novel telomere-interacting proteins, such as telomere-associated protein 1 (TelAP1), have recently been identified. Here, we used mass spectrometry-based proteomics and interactomics approaches, telomere pull-down assays with recombinant material and immunofluorescence analysis to elucidate the interactions of 21 other putative TelAPs. We investigated the influence on VSG expression and showed that depletion of TelAPs does not ultimately lead to changes in VSG expression. Additionally, we examined the interaction patterns of four TelAPs with the TbTRF/TbTIF2/TbRAP1 telomere complex by reciprocal affinity purification. We further propose that TelAP1 interacts with Tb927.6.4330, now called TelAP2, and that TelAP1 depends on this interaction to form a complex with the telomeric proteins TbTRF, TbTIF2 and TbRAP1.

microbiology↗

bioRxiv2022

ZNF524 directly interacts with telomeric DNA and supports telomere integrity

Telomeres are nucleoprotein structures at the ends of linear chromosomes. In humans, they consist of TTAGGG repeats, which are bound by dedicated proteins such as the shelterin complex. This complex blocks unwanted DNA damage repair at telomeres, e.g. by suppressing non-homologous end joining (NHEJ) through its subunit TRF2. We here describe ZNF524, a zinc finger protein that directly binds telomeric repeats with nanomolar affinity and reveal the base-specific sequence recognition by co-crystallization with telomeric DNA. ZNF524 localizes to telomeres and specifically maintains the presence of the TRF2/RAP1 subcomplex at telomeres without affecting other shelterin members. Loss of ZNF524 concomitantly results in an increase in DNA damage signaling and recombination events. Overall, ZNF524 is a direct telomere-binding protein involved in the maintenance of telomere integrity.

cell biology↗