Biology subjects

Osman, C.

Publications and source records attributed to Osman, C..

4 recordsLinked to original sources

bioRxiv2022

mtHsp70 converts mitochondrial proteostasis distress into impaired protein import

Functional mitochondria are essential for cell viability and depend on protein import from the cytosol. Impaired protein import initiates various well-characterized cellular programs that rescue or remove dysfunctional mitochondria. However, the molecular mechanism that underlies the initial reduction of protein import into defective mitochondria remained unknown. Here, we found that the redistribution of mtHsp70, mitochondrial chaperone that is involved in both protein import and protein folding, regulates the efficiency of protein import. During early mitochondrial stress, before rescue programs are initiated and membrane potential is affected, mtHsp70-dependent import was specifically impaired and association of mtHsp70 with the import complex reduced. Even under non-stress conditions, the majority of mtHsp70 is found in a substrate-bound state. We propose that the availability of free mtHsp70 limits protein import into mitochondria during stress.

biochemistry↗

bioRxiv2022

An improved MS2-MCP imaging system with minimal perturbation of mRNA stability

The MS2-MCP imaging system is widely used to study the mRNA spatial distribution in living cells. Here, we report that the MS2-MCP system may destabilize the tagged mRNA by targeting it to the nonsense-mediated mRNA decay pathway. We introduce an improved version, which has minimal perturbation of the mRNA stability.

cell biology↗

bioRxiv2021

Regulation with cell size ensures mitochondrial DNA homeostasis during cell growth

To maintain stable DNA concentrations, proliferating cells need to coordinate DNA replication with cell growth. For nuclear DNA, eukaryotic cells achieve this by coupling DNA replication to cell cycle progression, ensuring that DNA is doubled exactly once per cell cycle. By contrast, mitochondrial DNA replication is typically not strictly coupled to the cell cycle, leaving the open question of how cells maintain the correct amount of mitochondrial DNA during cell growth. Here, we show that in budding yeast, mitochondrial DNA copy number increases with cell volume, both in asynchronously cycling populations and during G1 arrest. Our findings suggest that cell-volume-dependent mitochondrial DNA maintenance is achieved through nuclear encoded limiting factors, including the mitochondrial DNA polymerase Mip1 and the packaging factor Abf2, whose amount increases in proportion to cell volume. By directly linking mitochondrial DNA maintenance to nuclear protein synthesis, and thus cell growth, constant mitochondrial DNA concentrations can be robustly maintained without a need for cell-cycle-dependent regulation.

cell biology↗

bioRxiv2021

YeastMate: Neural network-assisted segmentation of mating and budding events in S. cerevisiae

Here, we introduce YeastMate, a user-friendly deep learning-based application for automated detection and segmentation of Saccharomyces cerevisiae cells and their mating and budding events in microscopy images. We build upon Mask R-CNN with a custom segmentation head for the subclassification of mother and daughter cells during lifecycle transitions. YeastMate can be used directly as a Python library or through a stand-alone GUI application and a Fiji plugin as easy to use frontends. The source code for YeastMate is freely available at https://github.com/hoerlteam/YeastMate under the MIT license. We offer packaged installers for our whole software stack for Windows, macOS and Linux. A detailed user guide is available at https://yeastmate.readthedocs.io.

bioinformatics↗