Biology subjects

Bartoszewski, R.

Publications and source records attributed to Bartoszewski, R..

4 recordsLinked to original sources

bioRxiv2026

RBM25 selectively stabilizes XBP1s mRNA independently of splicing factor activity

The unfolded protein response (UPR) preserves endoplasmic reticulum (ER) proteostasis through coordinated transcriptional and translational programs that promote adaptation and prevents apoptosis. A central component of this response is the IRE1-XBP1 signaling axis, in which IRE1-mediated unconventional splicing of XBP1 mRNA generates the active transcription factor XBP1s. While the mechanisms governing IRE1 activation and XBP1 splicing have been extensively characterized, the post-transcriptional processes that sustain XBP1s expression remain poorly understood. Here, we identify RNA-binding motif protein 25 (RBM25) as a key post-transcriptional regulator of the UPR that selectively stabilizes spliced XBP1 mRNA during ER stress. RBM25 binds the XBP1s 3' untranslated region and prolongs XBP1s mRNA half-life without affecting unspliced XBP1u transcripts or IRE1-dependent regulated decay (RIDD) targets. Consequently, RBM25 depletion diminishes XBP1 transcriptional output, compromises adaptive UPR signaling, and sensitizes cells to ER stress-induced death across multiple stress paradigms. Together, our findings uncover a previously unrecognized RNA-based regulatory checkpoint that amplifies and sustains XBP1 signaling, thereby tuning the magnitude of the adaptive UPR and cellular survival under proteotoxic stress.

molecular biology↗

bioRxiv2026

HIF-1α coordinates adrenal steroidogenesis through direct transcriptional control and regulation of miRNA biogenesis

BackgroundAdrenal steroid hormone production is essential for systemic stress adaptation and metabolic homeostasis, and it is tightly regulated by oxygen availability. Previously, we demonstrated that acute hypoxia suppresses adrenal steroidogenesis through HIF-1-dependent induction of microRNAs (miRNAs) that target key steroidogenic enzymes. However, the mechanisms by which HIF-1 controls miRNA expression and activity in this context remain unclear. MethodsTo address this issue, we mapped the genome-wide HIF-1 binding landscape in murine adrenocortical cells using Cleavage Under Targets & Tagmentation (CUT&Tag). We integrated this data with gene expression analyses following pharmacological HIF-1 stabilization, physiological hypoxia, and genetic HIF-1 depletion to distinguish HIF-1-dependent effects from broader hypoxia-driven responses. ResultsWe detected HIF-1 binding at loci encoding steroidogenic enzymes and steroidogenesis-associated miRNAs. Unexpectedly, we also detected binding at genes involved in miRNA biogenesis and function, including components of the nuclear microprocessor complex and the cytoplasmic RNA-induced silencing complex (RISC). Functional analyses revealed that hypoxia broadly represses the expression of miRNA-processing genes through both HIF-1-dependent and -independent mechanisms. Notably, HIF-1 selectively modulated or counteracted this repression in a gene-specific manner, indicating a regulatory role beyond direct transcriptional activation. ConclusionsThese findings reveal an unrecognized layer of hypoxia-driven cell communication, wherein HIF-1 coordinates the transcriptional and post-transcriptional regulation of adrenal steroidogenesis by shaping the miRNA-processing landscape. This work extends our understanding of how oxygen-sensitive signaling pathways integrate gene expression and RNA-based regulatory mechanisms to control endocrine function.

molecular biology↗

bioRxiv2023

IRE1-mediated degradation of pre-miR-301a promotes apoptosis through upregulation of GADD45A

The unfolded protein response is a survival signaling pathway that is induced during various types of ER stress. Here we focus on the IRE1 pathway to determine IRE1s role in miRNA regulation during ER stress. During induction of ER stress in human bronchial epithelial cells, we utilized next generation sequencing to demonstrate that pre-miR-301a and pre-miR-106b, were significantly increased in the presence of an IRE1 inhibitor. Conversely, using nuclear-cytosolic fractionation on ER stressed cells, we found that these three pre-miRNAs were decreased in the nuclear fractions without the IRE1 inhibitor. We also found that miR-301a-3p targets the proapoptotic UPR factor, growth arrest and DNA-damage-inducible alpha (GADD45A). Inhibiting miR-301a-3p levels or blocking its predicted miRNA binding site in GADD45As 3 UTR with a target protector increased GADD45A mRNA expression. An elevation of XBP1s expression had no effect on GADD45A mRNA expression. We also demonstrated that the introduction of a target protector for the miR-301a-3p binding site in GADD45A mRNA during ER stress promoted cell death in the airway epithelial cells. These results indicated that IRE1s endonuclease activity is a two-edged sword that splices XBP1 mRNA for survival and degrades pre-miR-301a to elevate the mRNA expression of a pro-apoptotic gene, GADD45A.

cell biology↗

bioRxiv2018

Extracellular Adenine Nucleotide and Adenosine Metabolism in Calcific Aortic Valve Disease

Extracellular nucleotide catabolism contributes to immunomodulation, cell differentiation and tissue mineralization by controlling nucleotide and adenosine concentrations and its purinergic effects. Disturbances of purinergic signaling in valves may lead to its calcification. This study aimed to investigate the side-specific changes in extracellular nucleotide and adenosine metabolism in the aortic valve during calcific aortic valve disease (CAVD) and to identify the individual enzymes that are involved in these pathways as well as their cellular origin.\n\nStenotic aortic valves were characterized by reduced levels of extracellular ATP removal and impaired production of adenosine. Respectively, already reduced levels of extracellular adenosine were immediately degraded further due to the elevated rate of adenosine deamination. For the first time, we revealed that this metabolic pattern was observed only on the fibrosa surface of stenotic valve that is consistent with the mineral deposition on the aortic side of the valve. Furthermore, we demonstrated that non-stenotic valves expressed mostly ecto-nucleoside triphosphate diphosphohydrolase 1 (eNTPD1) and ecto-5nucleotidase (e5NT), while stenotic valves ecto-nucleotide pyrophosphatase/ phosphodiesterase 1, alkaline phosphatase and ecto-adenosine deaminase (eADA). On the surface of endothelial cells, isolated from non-stenotic valves, high activities of eNTPD1 and e5NT were found. Whereas, in valvular interstitial cells, eNPP1 activity was also detected. Stenotic valve immune infiltrate was an additional source of eADA. We demonstrated the presence of A1, A2a and A2b adenosine receptors in both, non-stenotic and stenotic valves with diminished expression of A2a and A2b in the former.\n\nExtracellular nucleotide and adenosine metabolism that involves complex ecto-enzyme pathways and adenosine receptor signaling were adversely modified in CAVD. In particular, diminished activities of eNTPD1 and e5NT with the increase in eADA that originated from valvular endothelial and interstitial cells as well as from immune inflitrate may affect aortic valve extracellular nucleotide concentrations to favor a proinflammatory milieu, highlighting a potential mechanism and target for CAVD therapy.

biochemistry↗