Biology subjects

Cipressa, F.

Publications and source records attributed to Cipressa, F..

3 recordsLinked to original sources

bioRxiv2025

An evolutionarily conserved role for separase in the regulation of nuclear lamins

Separase is a well conserved endopeptidase that facilitates sister chromatid separation at the metaphase-anaphase transition by cleaving cohesins. Beyond its role in chromosome segregation, Separase also participates in various biological processes, including chromatin organization and replication, centrosome disengagement and duplication, cytokinesis, and telomere capping. Here, we report that the loss of Drosophila separase (Sse) function induces significant changes in global protein expression and affects the protein levels of both A/C-type lamin C (LamC) and B-type lamin Dm0 (Dm0). We further demonstrate that SSE physically interacts with lamins and colocalizes with them at the nuclear envelope during interphase. Additionally, loss of SSE activity disrupts nuclear organization in larval muscles and impairs locomotion in adult flies. Notably, similar to SSE in flies, depletion of human separase (ESPL1) in SV40 fibroblasts leads to misshapen nuclei and increased levels of lamin A. Moreover, we show that ESPL1 interacts with lamin A in human fibroblasts, suggesting that the functional interaction between Separase and lamins is evolutionarily conserved across different organisms.

genetics↗

bioRxiv2024

Lamin B1-dependent regulation of human separase in mitosis

Separase plays a central role in chromosome separation during mitosis and in centrosome cycle. Tight control of separase activity is required to prevent unscheduled resolution of sister chromatid cohesion and centrosome aberrations, thereby preserving genome stability. In mammals, despite their disassembly in early mitosis, some nuclear envelope components possess mitotic roles, but links with separase activity remain unexplored. Here, we uncover a new mechanism of separase regulation involving lamin B1, a key nuclear envelope factor. We show that separase and lamin B1 associate preferentially during early stages of mitosis. Importantly, lamin B1 depletion leads to an increase in separase recruitment on chromosomes together with premature chromatid separation, a phenotype reminiscent of separase overexpression. Conversely, similar to separase depletion, lamin B1 overexpression induces formation of diplochromosomes- resulting from chromatid separation failure-, in association with centrosome amplification. Importantly, increasing separase level prevents lamin B1-induced centrosome aberrations, suggesting a separase defect at their origin. Indeed, we show that overexpression of lamin B1 leads to a decrease in the recruitment of separase to the chromosome and a delay in its activity. Taken together, this study unveils a novel mechanism of separase regulation involving the nuclear envelope factor lamin B1, that is crucial for genome integrity maintenance.

cell biology↗

bioRxiv2021

Low dose/dose rate γ irradiation protects Drosophila melanogaster chromosomes from double strand breaks and telomere fusions by modulating the expression of Loquacious.

It is still continuously debated whether the low-dose/dose-rate (LDR) of ionizing radiation represents a hazard for humans. Model organisms, such as fruit flies, are considered valuable systems to reveal insights into this issue. We found that, in wild-type Drosophila melanogaster larval neuroblasts, the frequency of Chromosome Breaks (CBs), induced by acute {gamma}-irradiation, is significantly reduced when flies are previously exposed to a protracted dose of 0.4Gy delivered at a dose rate of 2.5mGy/h. This indicates that this exposure, which is associated with an increased expression of DNA damage response proteins, induces a radioadaptive response (RAR) that protects Drosophila from extensive DNA damage. Interestingly, the same exposure reduces the frequency of telomere fusions (TFs) from Drosophila telomere capping mutants suggesting that the LDR can generally promote a protective response on chromatin sites that are recognized as DNA breaks. Deep RNA sequencing revealed that RAR is associated with a reduced expression of Loquacious D (Loqs-RD) gene that encodes a well-conserved dsRNA binding protein required for esiRNAs biogenesis. Remarkably, loss of Loqs mimics the LDR-mediated chromosome protection as it decreases the IR-induced CBs and TF frequency. Thus, our molecular characterization of RAR identifies Loqs as a key factor in the cellular response to LDR and unveils unprecedented epigenetic routes involved in radioresistance.

genetics↗