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Xrp1 governs the stress response program to spliceosome dysfunction

ABSTRACT: Unperturbed pre-mRNA splicing is crucial for proper expression of eukaryotic genes, but also maintenance of genome integrity. Loss of splicing factors is associated to DNA damage arising through different mechanisms, among which is the accumulation of mutagenic DNA/RNA hybrids (R-loops). RNase H1 recognizes and degrades the RNA moiety within R-loops, and is a commonly used marker for R-loops. Ecdysoneless protein was previously shown to participate in pre-mRNA splicing through its association with the U5 snRNP. In this study we have performed in vivo Targeted DamID using the Dam-RNase H1 construct to map the localization of R-loops throughout the Drosophila genome in control and Ecd-deficient Drosophila wing imaginal discs.

ORGANISM(S): Drosophila melanogaster

PROVIDER: GSE213325 | GEO | 2024/01/31

REPOSITORIES: GEO

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Project description:Strong cellular stress causes wide-spread perturbations in the transcriptome and in several types of DNA/RNA interactions, and through incompletely understood pathways to formation of cytoplasmic stress granules (SGs). We have investigated the relationships between strong transcriptional induction, RNA:DNA hybrid stretches (R-loops), and SG formation under severe hyperosmotic and glucose stress. Several mutations affecting DNA processing proteins, including the DNA polymerase subunit Pol32, confer SG formation defects. Severe stress increased R loop levels globally. We found that facilitating removal of R-loops by RNase H overexpression, with activity towards RNA:DNA hybrids, accelerated and enhanced transcriptional induction of stress-activated genes. Thus, overexpression of RNase H1, but not RNase H2, reduced R-loops globally around the 1 h mark. Remarkably, it also reduced SG formation. We performed a genome-wide analysis of the induction or repression kinetics of gene expression under severe stress conditions. RNase H1 overexpression reduced R-loops locally in highly transcribed stress-affected genes, as expected. Notably, it also increased expression of several stress-induced genes. Conversely, in cells where R-loops are not efficiently resolved, transcriptional induction of the same genes under stress was muted and occurred with a delay. Thus, in pol32∆ mutants, where SG accumulation is delayed, R-loop levels are elevated, and induction of stress genes suppressed. The pol32∆ mutants are also refractory to the effects of RNase H1 overexpression on stress gene induction, R-loop resolution, and SG formation, indicating that Pol32 may act downstream of Rnh1 in the regulation of these three processes. These findings demonstrate an unexpected link between R-loops and formation of SGs. Together, these observations indicate that under stress, strong transcriptional induction of specific genes or genomic regions causes R-loop accumulation, which then requires RNase H1 activity for resolution. If unresolved, the accumulated R-loops impede continued stress-induced transcription, and delay or prevent SG formation.

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Xrp1 governs the stress response program to spliceosome dysfunction

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