Biology subjects

Kukhtevich, I. V.

Publications and source records attributed to Kukhtevich, I. V..

4 recordsLinked to original sources

bioRxiv2026

Retrograde signalling mediates cellular adaptation to mitochondrial DNA copy number alterations

Eukaryotic cells maintain multiple copies of the mitochondrial genome, which is essential for cellular metabolism. Accordingly, alterations in the mitochondrial DNA (mtDNA) copy number are associated with severe human diseases and ageing. However, the mechanisms through which cells regulate mtDNA copy number and the cellular consequences of altered copy number remain poorly understood. Here, using budding yeast as a model, we show that mtDNA copy number is determined by the amount of three limiting factors, Mip1, Abf2, and Rim1. By synthetically tuning the concentrations of only these three proteins, we can modulate mtDNA dosage inside the cell. This revealed that cells are surprisingly robust to mtDNA copy number alterations, with increased copy numbers even accelerating cell growth. Our findings suggest that this robustness is due to protein dosage compensation and independent regulation of mitochondrial morphology. Mechanistically, we identified a critical role of the retrograde signalling pathway for this adaptation. We show that signalling from mitochondria to the nucleus is upregulated in cells with higher mtDNA copy number, and disruption of this regulation diminishes their faster growth. Taken together, our work reveals regulatory principles that enable cells to adapt to mtDNA copy number alterations.

cell biology↗

bioRxiv2024

Single-cell imaging reveals a key role of Bck2 in budding yeast cell size adaptation to nutrient challenges

Cell size is tightly controlled to optimize cell function and varies broadly depending on the organism, cell type, and environment. The budding yeast S. cerevisiae has been successfully used as a model to gain insights into eukaryotic cell size control. Multiple regulators of cell size in steady-state conditions have been identified, such as the G1/S transition activators Cln3 and Bck2 and the inhibitor Whi5. Individual deletions of these regulators result in populations with altered mean cell volumes. However, size homeostasis remains largely intact. Here, we show that although the roles of Bck2 and Cln3 for cell size regulation appear largely redundant in steady-state, a switch from fermentable to non-fermentable growth media reveals a unique role for Bck2 in cell size adaptation to changing nutrients. We use live-cell microscopy and machine learning-assisted image analysis to track single cells and their progeny through the nutrient switch. We find that after the switch, bck2{Delta} cells experience longer cell cycle arrests and more arrest-associated enlargement than wild-type, whi5{Delta} or cln3{Delta} cells, indicating that Bck2 becomes the critical G1/S activator in changing nutrients. Our work demonstrates that studying size regulation during nutrient shifts to mimic the dynamic environments of free-growing microorganisms can resolve apparent redundancies observed in steady-state size regulation.

cell biology↗

bioRxiv2021

Systematic identification of yeast mutants with increased rates of cell death reveals rapid stochastic necrosis associated with cell division

Cell death plays a major role in development, pathology and aging and can be triggered by various types of acute stimuli which arrest cell growth. However, little is known about chronic cell death in the context of continuing cell division. Here, we performed a genome-wide search for mutants with this type of death in dividing bakers yeast by assaying staining with phloxine B, which accumulates in dead cells. This screen yielded 83 essential and 43 non-essential gene mutants. Three contrasting types of spatial distribution of dead cells in colonies were observed, which corresponded to gene ontology enrichment for (i) DNA replication and repair, RNA processing, chromatin organization, and nuclear transport; (ii) mitosis and cytokinesis; and (iii) vesicular transport and glycosylation/cell wall homeostasis. To study dynamics of cell death in these mutants, we developed methods for analyzing the death of newborn cells (DON) and cell death in real time using microfluidics-based microscopy. These revealed rapid stochastic necrosis during bud generation or cytokinesis without prior division arrest. Increased death during division was associated with common sensitivity to plasma membrane and cell-wall perturbing agents, and could be mitigated by neutral pH stabilization of the medium. This suggests a common downstream type of cell death caused by a wide range of genetic perturbations.

cell biology↗

bioRxiv2020

Whi5 is diluted and protein synthesis does not dramatically increase in pre-Start G1

In their manuscript, Litsios et al.1 report a new model for how cell growth and biosynthetic activity control the G1/S transition in budding yeast. In essence, Litsios et al. claim that Start is driven by an increasing concentration of the G1 cyclin Cln3 due to a dramatic acceleration of protein synthesis in pre-Start G1 and not by the dilution of the cell cycle inhibitor Whi5. While we previously reported that Start was in part driven by cell growth during G1 diluting out the Start inhibitor Whi52, Litsios et al. report that Whi5 remains at constant concentration during G1, and changes in Whi5 concentration therefore do not contribute to Start. Since Litsios et al. directly contradict several key points of our own model of how cell growth triggers Start, we decided to investigate their claims and data. More specifically, we decided to investigate Litsios et al.s three major claims: O_LIWhi5 concentration remains constant during G1 C_LIO_LICln3 concentration strongly increases prior to Start C_LIO_LIGlobal protein synthesis rates increase by 2-3 fold prior to Start C_LI We investigated each of these three claims and found that the evidence presented by Litsios et al. does not support their claims due to inadequate analysis methods and flaws in their experiments.

molecular biology↗