Biology subjects

O'Neil, N. J.

Publications and source records attributed to O'Neil, N. J..

4 recordsLinked to original sources

bioRxiv2026

Heterologous expression of the human cohesin complex in Saccharomyces cerevisiae results in a dominant-negative phenotype

The cohesin complex has conserved roles in sister chromatid cohesion, DNA replication, genome organization, and the DNA damage response. We heterologously expressed the human cohesin complex in yeast to probe the behaviour of human cohesin. Human cohesin was unable to complement loss of function mutations in yeast cohesin, either as single subunits or as complexes, including in the context of co-expressing up to 12 human cohesin-associated genes. Heterologous expression of human cohesin in yeast expressing wildtype yeast cohesin resulted in dominant cohesion dysregulation and DNA damage sensitivity phenotypes. We used co-immunoprecipitation to demonstrate that human SMC proteins interact with endogenous yeast cohesin rings creating dominant-negative hybrid complexes that disrupt endogenous cohesin biology.

genetics↗

bioRxiv2025

The transsulfuration pathway suppresses the embryonic lethalphenotype of glutathione reductase mutants in Caenorhabditis elegans

The gsr-1 gene encodes the only glutathione reductase in Caenorhabditis elegans and gsr-1 loss of function alleles have a fully penetrant embryonic lethal phenotype. Therefore, maintenance of glutathione redox homeostasis is essential for nematode survival. We report here that impairment of the nonsense-mediated mRNA decay (NMD) pathway suppresses the embryonic lethality of gsr-1 mutants, allowing their normal development and growth. This NMD pathway dependent suppression requires cth-1 and cth-2 that encode, respectively, two isoforms of cystathionine-{gamma}-lyase that catalyze the conversion of cystathionine to cysteine through the transsulfuration pathway. Interestingly, the thioredoxin system that can also provide cysteine through the cystine reduction pathway is not required for the suppression of the lethal phenotype of gsr-1 embryos when the NMD pathway is inactivated. Together, our data indicate that increasing the activity of the reverse transsulfuration pathway can compensate the detrimental effect of the gsr-1 mutation, raising the interesting question of why C. elegans has not preserved such compensatory mechanism to avoid the embryonic lethality of these mutants. HighlightsO_LIA novel cryptic deletion in the smg-3 gene suppresses the embryonic lethality of C. elegans gsr-1 mutants. C_LIO_LIInactivation of the nonsense-mediated mRNA decay (NMD) pathway allows survival of gsr-1 mutant worms. C_LIO_LIGenetic impairment of the transsulfuration pathway restores the embryonic lethal phenotype in gsr-1; smg-3 mutants. C_LI

genetics↗

bioRxiv2019

Characterization of the phototoxicity, chemigenetic profile, and mutational signatures of the chemotherapeutic CX-5461 in Caenorhabditis elegans

New anti-cancer therapeutics require extensive in vivo characterization to identify endogenous and exogenous factors affecting efficacy, to measure toxicity and mutagenicity, and to determine genotypes resulting in therapeutic sensitivity or resistance. We used Caenorhabditis elegans as a platform with which to characterize properties of anti-cancer therapeutic agents in vivo. We generated a map of chemigenetic interactions between DNA damage response mutants and common DNA damaging agents. We used this map to investigate the properties of the new anti-cancer therapeutic CX-5461. We phenocopied the photoreactivity observed in CX-5461 clinical trials and found that CX-5461 generates reactive oxygen species when exposed to UVA radiation. We demonstrated that CX-5461 is a mutator, resulting in both large copy number variations and a high frequency of single nucleotide variations (SNVs). CX-5461-induced SNVs exhibited a distinct mutational signature. Consistent with the wide range of CX-5461-induced mutation types, we found that multiple repair pathways were needed for CX-5461 tolerance. Together, the data from C. elegans demonstrate that CX-5461 is a multimodal DNA damaging agent with strong similarity to ellipticines, a class of antineoplastic agents, and to anthracycline-based chemotherapeutics.

genetics↗

bioRxiv2017

Whole genome sequencing and assembly of a Caenorhabditis elegans genome with complex genomic rearrangements using the MinION sequencing device

Advances in 3rd generation sequencing have opened new possibilities for benchtop whole genome sequencing. The MinION is a portable device that uses nanopore technology and can sequence long DNA molecules. MinION long reads are well suited for sequencing and de novo assembly of complex genomes with large repetitive elements. Long reads also facilitate the identification of complex genomic rearrangements such as those observed in tumor genomes. To assess the feasibility of the de novo assembly of large complex genomes using both MinION and Illumina platforms, we sequenced the genome of a Caenorhabditis elegans strain that contains a complex acetaldehyde-induced rearrangement and a biolistic bombardment-mediated insertion of a GFP containing plasmid. Using [~]5.8 gigabases of MinION sequence data, we were able to assemble a C. elegans genome containing 145 contigs (N50 contig length = 1.22 Mb) that covered >99% of the 100,286,401 bp reference genome. In contrast, using [~]8.04 gigabases of Illumina sequence data, we were able to assemble a C. elegans genome in 38,645 contigs (N50 contig length = [~]26 kb) containing 117 Mb. From the MinION genome assembly we identified the complex structures of both the acetaldehyde-induced mutation and the biolistic-mediated insertion. To date, this is the largest genome to be assembled exclusively from MinION data and is the first demonstration that the long reads of MinION sequencing can be used for whole genome assembly of large (100 Mb) genomes and the elucidation of complex genomic rearrangements.

genomics↗