Biology subjects

Hollerer, I.

Publications and source records attributed to Hollerer, I..

3 recordsLinked to original sources

bioRxiv2026

Loss of UBP1 drives oxaliplatin resistance through a targetable dependency on translation initiation

Oxaliplatin is a common component of various chemotherapeutic regimens for the treatment of gastrointestinal cancers. However, the majority of patients exhibit resistance to oxaliplatin-based therapy. Here, we integrated knockout and transcription-activation CRISPR screens in patient-derived gastric cancer organoids (GC PDOs) to comprehensively profile major genetic and transcriptomic changes observed over the course of resistance acquisition. Our screens identified UBP1, a transcription factor frequently lost in GC, as a critical determinant of oxaliplatin resistance development. Leveraging a large GC organoid biobank from a co-clinical trial and primary tumor omics data, we reveal that downregulation of specifically MYC-driven ribosome biogenesis drives oxaliplatin resistance, highlighting the drugs role as a ribosome biogenesis stressor. Mechanistically, UBP1 loss reduced expression of its direct target, MAX, a MYC cofactor, leading to downregulation of ribosome biogenesis and protection against nucleolar stress. Crucially, we discover that such downregulation is inevitably followed by a compensatory reliance on translation initiation, making it a therapeutic vulnerability in oxaliplatin-resistant tumors. Consequently, the resistance could be overcome by a synergistic action of the translation initiation repressor 4EGI, and the effect was also maintained in PDO that acquired resistance in vivo under clinically relevant conditions. Our data uncover a common marker of oxaliplatin resistance and identify a novel therapeutic strategy to reverse resistance to one of the most frequently used anticancer drugs.

cancer biology↗

bioRxiv2021

Comprehensive analysis of meiosis-derived cDNA libraries reveals gene isoforms and mitochondrial proteins important for competitive fitness

Gametogenesis is a highly regulated and dynamic developmental program where a diploid progenitor cell differentiates into haploid gametes, the precursors for sexual reproduction. During meiosis, several pathways converge to initiate ploidy reduction and organelle remodelling to render gametes competent for zygote formation and subsequent organismal development. Additionally, meiosis inherently rejuvenates the newly formed gametes resulting in lifespan resetting. Here, we construct five stage-specific, inducible meiotic cDNA libraries that represent over 84% of the yeast genome. We employ computational strategies to detect stage-specific meiotic transcript isoforms in each library and develop a robust screening pipeline to test the effect of each cDNA on competitive fitness. Our multi-day proof-of-principle time course reveals gene isoforms that are important for competitive fitness as well as mitochondrial proteins that cause dose-dependent disruption of respiration. Together, these novel meiotic cDNA libraries provide an important resource for systematically studying meiotic genes and gene isoforms in future studies. HIGHLIGHTSO_LIConstruction of five stage-specific, inducible meiotic cDNA libraries in budding yeast that collectively represent 5563 genes, which is over 84% of the genome C_LIO_LIAnalysis of the cDNA libraries reveal the presence of meiosis-specific transcript isoforms that are largely uncharacterized C_LIO_LIDevelopment of a robust gain-of-function screening pipeline identifies previously characterized genes and novel gene isoforms important for competitive fitness C_LIO_LIMulti-day proof-of-principle screen reveals mitochondrial proteins that cause dosage-specific respiration defects C_LI

genetics↗

bioRxiv2018

mRNA expression-mediated gene repression in human cells

We recently described an unconventional mode of gene regulation in budding yeast by which transcriptional and translational interference were used in an integrated manner to down-regulate protein expression. Developmentally timed transcriptional interference inhibited production of a well translated mRNA isoform and resulted in the production of an mRNA isoform containing inhibitory upstream open reading frames (uORFs) that blocked translation of the ORF. Transcriptional interference and uORF-based translational repression are established mechanisms outside of yeast, but whether this type of integrated regulation was conserved was unknown. Here we find that, indeed, a similar type of regulation occurs at the locus for the human oncogene MDM2. We observe evidence of transcriptional interference between the two MDM2 promoters, which produce a poorly translated distal promoter-derived uORF-containing mRNA isoform and a well-translated proximal promoter-derived transcript. Down-regulation of distal promoter activity markedly up-regulates proximal promoter-driven expression and results in local reduction of histone H3K36 trimethylation. Moreover, we observe that this transcript toggling between the two MDM2 isoforms naturally occurs during human embryonic stem cell differentiation programs.

genetics↗