Mitotic BLM functions are required to maintain genomic stability
Ontology highlight
ABSTRACT:
PROVIDER: PRJEB88724 | ENA |
REPOSITORIES: ENA
Dataset's files
| Action | DRS | |||
|---|---|---|---|---|
| ERR14865200.fastq.gz | Fastqsanger.gz | |||
| ERR14865300.fastq.gz | Fastqsanger.gz | |||
| ERR14865400.fastq.gz | Fastqsanger.gz | |||
| ERR14865500.fastq.gz | Fastqsanger.gz | |||
| ERR14865201.fastq.gz | Fastqsanger.gz |
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Project description:The Bloom syndrome DNA helicase BLM contributes to chromosome stability through its roles in double-strand break repair by homologous recombination and DNA replication fork restart during the replication stress response. Loss of BLM activity leads to Bloom syndrome, which is characterized by extraordinary cancer risk and small stature. Here, we have analyzed the composition of the BLM complex in unperturbed cells and identified a direct physical interaction with the Mcm6 subunit of the minichromosome maintenance (MCM) complex by co-immunopecipitations using endogenous and recombinant proteins as well as two-hybrid analysis.
2022-02-15 | PXD018823 | Pride
Project description:Homologous recombination (HR) is an essential and highly regulated cellular process. Unintended HR in somatic cells is potentially deleterious; it can result in translocations and/or somatic cell loss of heterozygosity. This is suppressed by the BLM protein in combination with topoisomerase III, RMI1 and RMI2 in a hetero-tetrameric complex (the ‘Bloom’s complex’). To understand how the activities of BLM helicase and topoisomerase III are coupled, we purified the four-subunit complex. Chemical crosslinking and mass spectrometry revealed a unique architecture that couples helicase and topoisomerase domains.
2022-01-17 | PXD011078 | Pride
Project description:Replication fork reversal is a key protective mechanism against replication stress in higher eukaryotic cells and occurs via a series of coordinated enzymatic reactions. The Bloom syndrome gene product, BLM, is a member of the highly conserved RecQ helicase family and has been implicated in this process, but its precise regulation and role remain poorly understood. Here, we show that, upon replication stress, the GCFC domain-containing protein TFIP11 competes with the BLM helicase for association with stalled replication forks, thereby facilitates RAD51-mediated stalled fork reversal. Consequently, loss of TFIP11 results in aberrant accumulation of BLM at stalled forks, which in turn compromises RAD51 recruitment, impairs replication stress-induced fork reversal and slowing, hypersensitizes cells to replication stress-inducing agents, and enhances chromosomal instability. These findings reveal a previously unidentified regulatory mechanism that modulates the activities of BLM and RAD51 at stalled forks and thus genome integrity.
2024-05-24 | PXD042222 | Pride
Project description:Transcriptionally active loci are particularly prone to breakage and mounting evidence suggest that DNA Double-Strand Breaks arising in active genes are handled by a dedicated repair pathway, Transcription-Coupled DSB Repair (TC-DSBR), that entails R-loop accumulation and dissolution. Here, we uncovered a function for the Bloom RecQ DNA helicase (BLM) in TC-DSBR in human cells. BLM is recruited in a transcription dependent-manner at DSBs where it fosters resection, RAD51 binding and accurate Homologous Recombination repair. However, in an R-loop dissolution-deficient background, we found that BLM promotes cell death. We report that upon excessive R-loop accumulation, DNA synthesis is enhanced at DSBs, in a anner that depends on BLM and POLD3. Altogether our work unveils a role for BLM at DSBs in active chromatin, and highlights the toxic potential of RNA:DNA hybrids that accumulate at transcription-associated DSBs.
2022-04-13 | E-MTAB-11592 | biostudies-arrayexpress
Project description:Assessing the importance of BLM helicase upon DNA damage in the phosphorylation enhancement of DNA damage response (DDR) proteins via phosphoproteomic profiling in the presence and absence of BLM.
2025-05-06 | PXD048117 | Pride
Project description:Human TopBP1 is a key mediator protein involved in DNA replication checkpoint control. In this study, we report a specific interaction between TopBP1 and Bloom syndrome helicase (BLM) that is phosphorylation and cell-cycle dependent. Interestingly, TopBP1 depletion led to decreased BLM protein level and increased sister chromatid exchange (SCE). Moreover, our data indicated that BLM was ubiquitinated by E3 ligase MIB1 and degraded in G1 cells but was stabilized by TopBP1 in S phase cells. Depletion of MIB1 restored BLM protein level and rescued the elevated SCE phenotype in TopBP1-depleted cells. In addition, cells expressing an undegradable BLM mutant showed radiation sensitivity, probably by triggering end resection and inhibiting the nonhomologous end-joining (NHEJ) pathway in G1 phase. Altogether, these data suggest that, although BLM is downregulated in G1 phase in order to promote NHEJ-mediated DNA repair, it is stabilized by TopBP1 in S phase cells in order to suppress SCE and thereby prevent genomic instability.
| S-EPMC3880544 | biostudies-literature
Project description:Bloom’s syndrome (BLM) protein is a known nuclear helicase that is able to unwind DNA secondary structures such as G-quadruplexes. However, its role in the regulation of cytoplasmic processes that involve RNA G-quadruplexes (rG4s) has not been previously studied. Here, we demonstrate that BLM is recruited to stress granules (SGs), which are cytoplasmic biomolecular condensates composed of RNA-binding proteins and RNAs. BLM is enriched in SGs upon different stress conditions and in an rG4-dependent manner. We show that BLM unwinds rG4s efficiently, thus acting as a negative regulator of SG formation, potentially via its unwinding function. Altogether, our data expand the cellular activity of BLM and shed light on the function that helicases play in the dynamics of biomolecular condensates.
2023-10-24 | PXD039534 | Pride
Project description:The Bloom syndrome helicase BLM and topoisomerase-IIβ-binding protein 1 (TopBP1) are key regulators of genome stability. It was recently proposed that BLM phosphorylation on Ser338 mediates its interaction with TopBP1, to protect BLM from ubiquitylation and degradation (Wang et al., 2013). Here, we show that the BLM-TopBP1 interaction does not involve Ser338 but instead requires BLM phosphorylation on Ser304. Furthermore, we establish that disrupting this interaction does not markedly affect BLM stability. However, BLM-TopBP1 binding is important for maintaining genome integrity, because in its absence cells display increased sister chromatid exchanges, replication origin firing and chromosomal aberrations. Therefore, the BLM-TopBP1 interaction maintains genome stability not by controlling BLM protein levels, but via another as-yet undetermined mechanism. Finally, we identify critical residues that mediate interactions between TopBP1 and MDC1, and between BLM and TOP3A/RMI1/RMI2. Taken together, our findings provide molecular insights into a key tumor suppressor and genome stability network.
| S-EPMC4374139 | biostudies-literature
Project description:Genome modification in mouse embryonic stem cells (mESCs) has provided the versatile platform to analyzing gene functions in mammalian cells. Bloom helicase-deficient mESCs showed elevated rate of loss of heterozygosity (LOH) through mitotic recombination. By utilizing this characteristic of Blm deficiency, we established an efficient method to introduce homozygous mutations into mESCs, which can be used for phenotype-driven recessive screen. It is generally thought that mitotic recombination is initiated by double-strand break. DNA repair machinery, however, possesses mechanisms that suppress deleterious crossovers between homologous chromosomes. Bloom helicase plays a central role to suppress such crossover; hence its deficiency causes elevated frequency of mitotic recombination. To directly answer if DSB can initiate mitotic recombination, we established a reporter cell line, in which the recognition site of I-SceI endonuclease was introduced in the Aprt gene in Blm-deficient mESCs. We used two types of I-SceI expression vectors; one expresses a mammalian codon-optimized I-SceI (ISceIo) and the other expresses I-SceIo fused with N-terminal 110-amino acids of Geminin (Gemi). Geminin-fused I-SceI can be stabilized only in lateS/G2 phase. After I-SceI transfection and subsequent selection, we isolated Aprt-deficient mutants. Half of the mutants showed LOH in the whole telomeric region from I-SceI site, but the other half showed local LOH near the I-SceI site. Further analyses suggested that large deletion was introduced and caused LOH, which was not seen in spontaneous LOH. We designed CGH probes in 300-bp resolution in 8Mb telomeric region of chr 8 (The Aprt gene locates 7Mb from the telomere) to map the deleted regions in these mutants.
2012-11-30 | E-MTAB-1116 | biostudies-arrayexpress
Project description:Spindle assembly checkpoint (SAC) ensures bipolar attachment of chromosomes to the mitotic spindle and is essential for faithful chromosome segregation, thereby preventing chromosome instability (CIN). Genetic evidence suggests a causal link between compromised SAC, CIN, and cancer. Bloom syndrome (BS) is a genetic disorder that predisposes affected individuals to cancer. BS cells exhibit elevated rates of sister chromatid exchange, chromosome breaks, and CIN. The BS gene product, BLM, is a member of the RecQ helicases that are required for maintenance of genome stability. The BLM helicase interacts with proteins involved in DNA replication, recombination, and repair and is required for the repair of stalled-replication forks and in the DNA damage response. Here we present biochemical evidence to suggest a role of BLM phosphorylation during mitosis in maintaining chromosome stability. BLM is associated with the SAC kinase MPS1 and is phosphorylated at S144 in a MPS1-dependent manner. Phosphorylated BLM interacts with polo-like kinase 1, a mitotic kinase that binds to phosphoserine/threonine through its polo-box domain (PBD). Furthermore, BS cells expressing BLM-S144A show normal levels of sister chromatid exchange but fail to maintain the mitotic arrest when SAC is activated and exhibit a broad distribution of chromosome numbers. We propose that MPS1-dependent BLM phosphorylation is important for ensuring accurate chromosome segregation, and its deregulation may contribute to cancer.
| S-EPMC1518802 | biostudies-literature