Biology subjects

Shipkovenska, G.

Publications and source records attributed to Shipkovenska, G..

5 recordsLinked to original sources

bioRxiv2025

Principles of protein abundance regulation across single cells in a mammalian tissue

Protein synthesis and clearance are major regulatory steps of gene expression, but their in vivo regulatory roles across the cells comprising complex tissues remains unexplored. Here, we systematically quantify protein synthesis and clearance across over 4,200 cells from a primary tissue. Through integration with single-cell transcriptomics, we report the first quantitative analysis of how individual cell types regulate their proteomes across the continuum of gene expression. Our analysis quantifies the relative contributions of RNA abundance, translation, and protein clearance to the abundance variation of thousands of proteins. These results reveal a putative organizing principle: The contributions of both translation and protein clearance are linearly dependent on the cell growth rate. Further, we find that some proteins are primarily regulated by one mechanism (RNA abundance, translation, or clearance) across all cell types while the dominant regulation of other proteins is cell-type specific. Age related changes in protein abundance are cell-type specific and correlated to changes in protein clearance. Our reliable multimodal measurements enabled quantifying and functionally interpreting molecular variation across single cells from the same cell type. The protein-protein correlations are substantially stronger than the mRNA-mRNA ones both for directly interacting proteins and for functional protein sets. This difference is mediated by protein clearance regulation. Further, the protein correlations allow identifying cell-type specific functional clusters. These clusters vary across cell types, revealing differences in metabolic processes coordination, partially regulated by protein degradation. Our approach reveals organizing principles determining the relative contributions of translation and protein clearance and provides a scalable framework for investigating protein regulation in mammalian tissues.

systems biology↗

bioRxiv2025

The identification and characterization of hillocks in the postnatal mouse and human airway

Adult lung regeneration has been deeply scrutinized over the past decade. In contrast, the injury resistance mechanisms of the neonatal and pediatric airway have received considerably less attention despite the manifest clinical importance. We recently reported the discovery of the airway hillock in adult murine and human airways. Adult hillocks are stratified structures with luminal squamous barrier cells overlying a dedicated basal stem cell population. Functionally, hillocks serve as an injury-resistant reservoir of dedicated hillock stem cells that can resurface and repopulate the airway epithelium after severe damage. Indeed, hillock basal stem cells undergo massive clonal expansion in the process of repopulating denuded airway epithelium. Since the postnatal lung encounters injuries that can result in airway epithelial denudation in the setting of respiratory infection or aspiration, we sought to assess whether hillocks are present in the neonatal airway. In this manuscript we identify and characterize hillocks in postnatal mouse and human pediatric airways. We show that hillocks are present in mice from postnatal day 3 onwards and that they expand in size through adulthood. The earliest hillocks are functionally immature, but they acquire their injury resistance properties over the course of postnatal maturation. By re-analyzing published pediatric scRNAseq data, we identify cells with a hillock squamous cell gene signature that is conserved across species. Finally, we identify bona fide hillocks in an 8-month-old infant and an 8-year-old child. We now wonder whether the presence and maturation of hillocks has implications for disorders of the neonatal and childhood airway. More specifically, we hypothesize that the incomplete maturation of hillocks could create a window of vulnerability in neonates who may be particularly susceptible to airway damage in the setting of infection or aspiration. Thus, there is a need to define when human hillocks first form and establish the time window during which they functionally mature as a prelude to determining whether the appearance and properties of hillocks correlate to clinical phenotypes and outcomes.

developmental biology↗

bioRxiv2024

Limiting the impact of protein leakage in single-cell proteomics

Limiting artifacts during sample preparation can significantly increase data quality in single-cell proteomics experiments. Towards this goal, we characterize the impact of protein leakage by analyzing thousands of primary single cells that were prepared either fresh immediately after dissociation or cryopreserved and prepared at a later date. We directly identify permeabilized cells and use the data to define a signature for protein leakage. We use this signature to build a classifier for identifying damaged cells that performs accurately across cell types and species.

molecular biology↗

bioRxiv2019

An RNA degradation complex required for silencing of Polycomb target genes

Polycomb Repressive Complex (PRC) 1 and 2 are histone-modifying and chromatin-binding complexes that are required for silencing of developmental regulatory genes and genes that control cellular proliferation. Their gene silencing functions are thought to involve chromatin compaction and condensate formation but whether other mechanisms contribute to silencing is unknown. Here we show that the rixosome, a conserved RNA degradation complex with roles in ribosomal RNA processing and heterochromatic RNA degradation in fission yeast, associates with human PRC complexes, is recruited to promoters of Polycomb target genes in differentiated cell lines and embryonic stem cells, and is required for efficient silencing of Polycomb target genes. These findings reveal an unanticipated role for RNA degradation in Polycomb-mediated silencing.

molecular biology↗

bioRxiv2019

An RNA Degradation Complex Required for Spreading and Epigenetic Inheritance of Heterochromatin

Heterochromatin assembly requires the methylation of histone H3 lysine 9 by the Clr4(Suv39h) methyltransferase and both the spreading and epigenetic inheritance of heterochromatin involve the recognition of H3K9me-containing nucleosomes by Clr4 and catalysis of H3K9me on adjacent nucleosomes. How this read-write mechanism overcomes obstacles posed by RNA polymerase II and nascent RNA in its path is not fully understood. Here we identify a role for the highly conserved and essential Rix1-containing complex (here referred to as the rixosome), with known RNA endonuclease and polynucleotide kinase activities required for ribosomal RNA (rRNA) processing, in spreading and epigenetic inheritance of heterochromatin. Viable mutations in rixosome subunits that disrupt its association with Swi6/HP1 fail to localize to heterochromatin, lead to accumulation of heterochromatic RNAs, and block spreading of H3K9me and silencing away from nucleation sites into actively transcribed regions. These findings reveal a new pathway for degradation of heterochromatic RNAs with essential roles in heterochromatin spreading and inheritance.

molecular biology↗