Biology subjects

Tanny, J.

Publications and source records attributed to Tanny, J..

4 recordsLinked to original sources

bioRxiv2023

The Rtf1/Prf1-dependent histone modification axis and Rpb1 C-terminal domain phosphorylation counteract multi-drug resistance in fission yeast

AbstractRNA polymerase II (RNAPII) transcription elongation directs an intricate pattern of histone modifications. Formation of this pattern involves a highly conserved regulatory axis, key components of which are the elongation factor Rtf1, monoubiquitylation of histone H2B (H2Bub1), and methylation of histone H3 on lysine 4 (H3K4me). Direct contact between Rtf1 and the ubiquitylation complex Rad6-Bre1 stimulates H2Bub1, which in turn promotes H3K4me by stimulating the activity of the Set1C/COMPASS methyltransferase complex. Previous studies have defined the molecular basis for these regulatory relationships, but it remains unclear how they regulate chromatin and transcription in vivo. We found that mutations affecting multiple components of the Rtf1-H2Bub1-H3K4me axis in the model eukaryote Schizosaccharomyces pombe (fission yeast) caused resistance to the ribonucleotide reductase inhibitor hydroxyurea (HU). Resistance correlated with a reduced effect of HU on dNTP pools, bypass of the S-phase checkpoint in the presence of HU, and blunting of the transcriptional response to HU treatment. Mutations in the C-terminal repeat domain (CTD) of the RNAPII large subunit Rpb1 led to a similar spectrum of phenotypes. Moreover, all the HU resistant mutants we identified also exhibited resistance to several azole class antifungal agents. Our results suggest a novel, shared gene regulatory function of the Rtf1-H2Bub1-H3K4me axis and the Rpb1 CTD in controlling fungal drug tolerance.

molecular biology↗

bioRxiv2021

Single cell analysis of population-wide nuclear and cytosolic drug responses using high-content FRET imaging: measuring protein kinase activation in rat primary striatal neurons

Genetically-encoded biosensors are used to track biochemical activities in living cells by measuring changes in fluorescence emitted by one or more fluorescent proteins. In the present article, we describe the application of genetically-encoded FRET biosensors with high content microscopy to image the signaling responses of thousands of neurons in response to drug treatments. We applied this approach to reveal intercellular variation in signaling responses among cultured striatal neurons stimulated with multiple drugs. The striatum is largely composed of medium-spiny GABAergic neurons which are divided into two broad sub-types based in part on their expression of dopamine D1 vs. D2 receptors. Using high content FRET imaging and immunofluorescence, we identified neuronal sub-populations with unique responses to pharmacological manipulation. Focusing on dopamine- and glutamate-regulated PKA and ERK1/2 signaling in both the cytoplasm and nucleus, we identified pronounced intercellular differences, in both the magnitude and kinetics of signaling responses to drug application. Importantly, we found that a conventional "bulk" analysis that included all cells in culture yielded a different rank order of drug potency than that revealed by our single-cell analysis. The high degree of heterogeneity that we observed at the single cell level would not have been detectable using common population-level analyses, derived for example from western blotting or plate reader-based measurements. In conclusion, our single-cell analytical approach highlights the limitations of population-level analyses, and provides a novel way to study signaling biology.

neuroscience↗

bioRxiv2017

Cdk9, Spt5 and histone H2B mono-ubiquitylation cooperate to ensure antisense suppression by the Clr6-CII/Rpd3S HDAC complex

Cyclin-dependent kinase 9 (Cdk9) and histone H2B monoubiquitylation (H2Bub1) are both implicated in elongation by RNA polymerase II (RNAPII). In fission yeast, Cdk9 and H2Bub1 regulate each other through a feedback loop involving phosphorylation of the elongation factor Spt5. Conversely, genetic interactions suggest opposing functions of H2Bub1 and Cdk9 through an Spt5-independent pathway. To understand these interactions, we performed RNA-seq analysis after H2Bub1 loss, Cdk9 inhibition, or both. Either Cdk9 inhibition or H2Bub1 loss increased levels of antisense transcription initiating within coding regions of distinct subsets of genes; ablation of both pathways led to antisense derepression affecting over half the genome. Cdk9 and H2Bub1 cooperate to suppress antisense transcription by promoting function of the Clr6-CII histone deacetylase (HDAC) complex. H2Bub1 plays a second role, in opposition to Clr6-CII, to promote sense transcription in subtelomeric regions. Therefore, functional genomics revealed both collaborative and antagonistic functions of H2Bub1 and Cdk9.

molecular biology↗

bioRxiv2016

Histone gene expression is regulated by histone H2B ubiquitylation in fission yeast

Cell cycle-regulated expression of histone genes is vital for coordination of DNA replication with chromatin assembly. In yeast, histone genes are regulated by transcriptional activation in S phase and transcriptional repression in other phases of the cell cycle, although the mechanisms are poorly understood. Here we describe a role for histone H2B monoubiquitylation (H2Bub1), a histone mark that is linked to RNA polymerase II transcription elongation, in the activation of replication-dependent histone genes in the fission yeast Schizosaccharomyces pombe. Loss of H2Bub1 is also associated with a delay in S phase progression and reduced expression of the replication initiation factor Cdc18 (ortholog of Cdc6). We provide evidence that H2Bub1 impacts histone gene transcription and acts through a mechanism that involves the 3UTR. Consistent with our previous finding that H2Bub1 is functionally opposed to the elongation factor Cdk9, we also find that the effects of H2Bub1 on histone genes are suppressed by reduction in the activity of Cdk9. Our data suggest that H2Bub1 promotes cell growth by activating cell cycle-regulated genes.

molecular biology↗