Biology subjects

Novarina, D.

Publications and source records attributed to Novarina, D..

5 recordsLinked to original sources

bioRxiv2026

The role of the nuclear pore complex in the stability of disease-related short tandem DNA repeats

Nuclear pore complexes (NPCs) mediate selective transport between the nucleus and the cytoplasm, but also contribute to maintaining genome stability. Mutations in NPC genes cause genome instability and sensitivity to DNA damaging agents, and DNA that is difficult to repair or replicate relocates to NPCs, including expanded CAG repeats, which are associated with several neurological diseases. Here, we show that other disease-related short tandem repeats also relocate to NPCs. Relocation depends on the NPC basket protein Nup1, but is independent of the rest of the basket. Abrogating relocation to the NPC increases rates of repeat contraction, but not expansion. By contrast, deletion of the basket component NUP60, which causes mislocalization of all other basket proteins except Nup1, results in greater genome instability without affecting relocation to NPCs. Our results show that NPC association is a general feature of disease-related short tandem repeats, and suggest that relocation to NPCs is separable from the other genome maintenance functions of the NPC basket.

cell biology↗

bioRxiv2024

Revisiting the role of the spindle assembly checkpoint in the formation of gross chromosomal rearrangements in Saccharomyces cerevisiae

Multiple pathways are known to suppress the formation of gross chromosomal rearrangements (GCRs), which can cause human diseases including cancer. In contrast, much less is known about pathways that promote their formation. The spindle assembly checkpoint (SAC), which ensures the proper separation of chromosomes during mitosis, has been reported to promote GCR, possibly by delaying mitosis to allow GCR-inducing DNA repair to occur. Here we show that this conclusion is the result of an experimental artifact arising from the synthetic lethality caused by disruption of the SAC and loss of the CIN8 gene, which is often lost in the genetic assay used to select for GCRs. After correcting for this artifact, we find no role of the SAC in promoting GCR. Significance statementA gross chromosomal rearrangement (GCR) is an abnormal structural change of a native chromosome. Examples of GCRs include deletions, duplications, inversions, and translocations. GCRs can lead to genetic diseases such as cancer. A previous study implicated the spindle assembly checkpoint (SAC), which ensures the proper separation of chromosomes during cell division, in facilitating the formation of GCRs. In this study, we show that this is not the case; the SAC does not promote GCR.

molecular biology↗

bioRxiv2021

Vacuolar localization via the N-terminal domain of Sch9 is required for TORC1-dependent phosphorylation and downstream signal transduction

The budding yeast Sch9 kinase (functional ortholog of the mammalian S6 kinase) is a major effector of the Target of Rapamycin Complex 1 (TORC1) complex in the regulation of cell growth in response to nutrient availability and stress. In budding yeast, Sch9 is partially localized at the vacuolar surface, where it is phosphorylated by TORC1 under favorable growth conditions. Sch9 recruitment at the vacuole is mediated by direct interaction between PI(3,5)P2 on the vacuolar membrane and the region of Sch9 encompassing amino acid residues 1-390, which contains a C2 domain. Since many C2 domains mediate phospholipid binding, it had been suggested that the C2 domain of Sch9 mediates its vacuolar recruitment. However, the in vivo requirement of the C2 domain for Sch9 localization had not been demonstrated, and the phenotypic consequences of Sch9 delocalization remained unknown. Here, by examining cellular localization, phosphorylation state and growth phenotypes of Sch9 truncation mutants, we show that deletion of the N-terminal domain of Sch9 (aa 1-182), but not the C2 domain (aa 183-399), impairs vacuolar localization and TORC1-dependent phosphorylation of Sch9, while causing growth defects similar those observed in sch9{Delta} cells. Artificial tethering of an N-terminally truncated Sch9 mutant at the vacuolar membrane rescued TORC1-dependent phosphorylation and cell growth. Our study uncovers a key role for the N-terminal domain of Sch9 and demonstrates that recruitment of Sch9 at the vacuolar surface is necessary for TORC1-dependent phosphorylation and downstream signal transduction for the regulation of cell growth.

cell biology↗

bioRxiv2020

A genome-wide screen for genes affecting spontaneous direct-repeat recombination in Saccharomyces cerevisiae

Homologous recombination is an important mechanism for genome integrity maintenance, and several homologous recombination genes are mutated in various cancers and cancer-prone syndromes. However, since in some cases homologous recombination can lead to mutagenic outcomes, this pathway must be tightly regulated, and mitotic hyper-recombination is a hallmark of genomic instability. We performed two screens in Saccharomyces cerevisiae for genes that, when deleted, cause hyper-recombination between direct repeats. One was performed with the classical patch and replica-plating method. The other was performed with a high-throughput replica-pinning technique that was designed to detect low-frequency events. This approach allowed us to validate the high-throughput replica-pinning methodology independently of the replicative aging context in which it was developed. Furthermore, by combining the two approaches, we were able to identify and validate 35 genes whose deletion causes elevated spontaneous direct-repeat recombination. Among these are mismatch repair genes, the Sgs1-Top3-Rmi1 complex, the RNase H2 complex, genes involved in the oxidative stress response, and a number of other DNA replication, repair and recombination genes. Since several of our hits are evolutionary conserved, and repeated elements constitute a significant fraction of mammalian genomes, our work might be relevant for understanding genome integrity maintenance in humans.

genomics↗

bioRxiv2018

A genome-wide screen identifies genes that suppress the accumulation of spontaneous mutations in young and aged yeast cells

To ensure proper transmission of genetic information, cells need to preserve and faithfully replicate their genome, and failure to do so leads to genome instability, a hallmark of both cancer and aging. Defects in genes involved in guarding genome stability cause several human progeroid syndromes, and an age-dependent accumulation of mutations has been observed in different organisms, from yeast to mammals. However, it is unclear if the spontaneous mutation rate changes during aging, and if specific pathways are important for genome maintenance in old cells. We developed a high-throughput replica-pinning approach to screen for genes important to suppress the accumulation of spontaneous mutations during yeast replicative aging. We found 13 known mutation suppression genes, and 31 genes that had no previous link to spontaneous mutagenesis, and all acted independently of age. Importantly, we identified PEX19, encoding an evolutionarily conserved peroxisome biogenesis factor, as an age-specific mutation suppression gene. While wild-type and pex19{Delta} young cells have similar spontaneous mutation rates, aged cells lacking PEX19 display an elevated mutation rate. This finding suggests that functional peroxisomes are important to preserve genome integrity specifically in old cells, possibly due to their role in reactive oxygen species metabolism.\n\nAuthor SummarySpontaneous mutations arise as a consequence of improper repair of DNA damage caused by intracellular (i.e. toxic by-products of normal cellular metabolism or inaccurate DNA replication) or external (e.g. UV light or chemotherapy) sources. Elevated mutagenesis is implicated in tumorigenesis, and an age-dependent accumulation of mutations has been observed in many organisms. However, it is still unclear how and at which rate mutations accumulate during aging. It is also unknown if specific mechanisms exist that protect the genome of aged cells. We developed a high-throughput, genome-wide approach to identify genes that suppress the accumulation of mutations during yeast replicative aging. Yeast replicative aging refers to the decline in viability a single cell experiences with increasing number of mitotic divisions. We identified a number of new genes that counteract the accumulation of mutations independently of age. Moreover, we discovered that PEX19, a gene involved in the biogenesis of peroxisomes, is important to prevent the accumulation of mutations in aged cells. Since PEX19 is conserved in humans, our work might help understand how human cells could better protect their genome from mutations during aging.

genetics↗