Biology subjects

Luscher, B.

Publications and source records attributed to Luscher, B..

7 recordsLinked to original sources

bioRxiv2026

Reversing PROTAC-induced ASH2L degradation reactivates proliferation in senescent cells

Nucleosomes control access to gene promoters. Histone H3 lysine 4 tri-methylation, catalyzed by 6 KMT2 complexes, correlates with accessible promoters and gene expression. The catalytic activity of KMT2 enzymes depends on an obligatory core complex with ASH2L being an essential subunit. We find that PROTAC induced depletion of ASH2L reduces H3K4me3, deregulates gene expression and prevents proliferation. Upon prolonged ASH2L loss, cells develop a senescent phenotype, a process linked to aging and disease. Competing the PROTAC reactivates ASH2L, reestablishes H3K4me3 at promoters and reverts gene expression changes. Cells reenter the cell cycle and resume proliferation, thereby reverting senescence. Structure-function studies demonstrate that these molecular and cellular consequences are primarily due to the loss of ASH2L functions associated with KMT2 complexes. Together, these findings indicate that stress inflicted by the loss of KMT2 catalytic activities promotes a reversible senescence phenotype, suggesting that the functions of KMT2 complexes are implicated in aging. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=127 SRC="FIGDIR/small/722411v1_ufig1.gif" ALT="Figure 1"> View larger version (30K): org.highwire.dtl.DTLVardef@10ace2forg.highwire.dtl.DTLVardef@667c81org.highwire.dtl.DTLVardef@78039dorg.highwire.dtl.DTLVardef@13563be_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2026

Human PARPs modify RNA nucleobases in vitro and in cells

ADP-ribosylation is known as a protein modification, yet recent studies have expanded the range of ADP-ribosyltransferase (ART) substrates to include nucleic acids. tRNA 2'-phosphotransferase 1 (TRPT1) and several PARP family members can modify the 5'-phosphate of single-stranded RNA. Here, we show that PARP10 and PARP15 extend this activity beyond the 5'-phosphate terminus and generate N3-ADP-ribosyl uracil and N1-ADP-ribosyl guanine bases. The base-linked ADP-ribosylation is reversed selectively by the macrodomain-containing hydrolase TARG1. In TARG1 knockout cells, N1-ADP-ribosyl guanine can be detected. Together, these findings establish guanine and uracil ADP-ribose as two novel nucleotide modifications and reveal PARP15 and TARG1 as an enzyme pair which can dynamically regulate guanine ADP-ribosylation in living cells.

biochemistry↗

bioRxiv2025

Dimerization of human PARP15 is required for NAD+ binding and automodification

PARP proteins are enzymes catalyzing ADP-ribosylation, a well-conserved post-translational modification. In addition to the catalytic domain present in all PARPs, these proteins have a wide selection of other domains possessing different functions. Additional domains present in human PARP15 are macrodomains, capable of binding ADP-ribose. PARP15 is the least studied of the macrodomain-containing human PARPs, and it is linked to different diseases from infections to cancer. We show that the full-length canonical isoform 1 of PARP15 auto-ADP-ribosylates robustly on glutamate and aspartate residues, which can be hydrolyzed by known ADP-ribosylhydrolases. We have been able to locate several modification sites to the region of tandem macrodomains. In agreement with earlier reports regarding the catalytic domain dimerization being the requirement for enzyme activity, we show this in the full-length context with the recombinant isoform 1 of PARP15. We show that dimerization is required for the efficient substrate NAD+ binding, and we provide structural basis for this requirement with the help of a co-crystal structure of the catalytic domain dimer with an unhydrolyzable substrate analog.

biochemistry↗

bioRxiv2024

Transcriptome signatures of the medial prefrontal cortex underlying GABAergic control of resilience to chronic stress exposure

Analyses of postmortem human brains and preclinical studies of rodents have identified somatostatin (SST)-positive interneurons as key elements that regulate the vulnerability to stress-related psychiatric disorders. Conversely, genetically induced disinhibition of SST neurons or brain region-specific chemogenetic activation of SST neurons in mice results in stress resilience. Here, we used RNA sequencing of mice with disinhibited SST neurons to characterize the transcriptome changes underlying GABAergic control of stress resilience. We found that stress resilience of male but not female mice with disinhibited SST neurons is characterized by resilience to chronic stress-induced transcriptome changes in the medial prefrontal cortex. Interestingly, the transcriptome of non-stressed stress-resilient male mice resembled the transcriptome of chronic stress-exposed stress-vulnerable mice. However, the behavior and the serum corticosterone levels of non-stressed stress-resilient mice showed no signs of physiological stress. Most strikingly, chronic stress exposure of stress-resilient mice was associated with an almost complete reversal of their chronic stress-like transcriptome signature, along with pathway changes indicating stress-induced enhancement of mRNA translation. Behaviorally, the mice with disinhibited SST neurons were not only resilient to chronic stress-induced anhedonia -- they also showed an inversed anxiolytic-like response to chronic stress exposure that mirrored the chronic stress-induced reversal of the chronic stress-like transcriptome signature. We conclude that GABAergic dendritic inhibition by SST neurons exerts bidirectional control over behavioral vulnerability and resilience to chronic stress exposure that is mirrored in bidirectional changes in expression of putative stress resilience genes, through a sex-specific brain substrate.

neuroscience↗

bioRxiv2024

Sex-specific GABAergic microcircuits that switch vulnerability into resilience to stress and reverse the effects of chronic stress exposure

Clinical and preclinical studies have identified somatostatin (SST)-positive interneurons as key elements that regulate the vulnerability to stress-related psychiatric disorders. Conversely, disinhibition of SST neurons in mice results in resilience to the behavioral effects of chronic stress. Here we established a low-dose chronic chemogenetic protocol to map these changes in positively and negatively motivated behaviors to specific brain regions. AAV-hM3Dq mediated chronic activation of SST neurons in the prelimbic cortex (PLC) had antidepressant drug-like effects on anxiety- and anhedonia-like motivated behaviors in male but not female mice. Analogous manipulation of the ventral hippocampus (vHPC) had such effects in female but not male mice. Moreover, activation of SST neurons in the PLC of male and the vHPC of female mice resulted in stress resilience. Activation of SST neurons in the PLC reversed prior chronic stress-induced defects in motivated behavior in males but was ineffective in females. Conversely, activation of SST neurons in the vHPC reversed chronic stress-induced behavioral alterations in females but not males. Quantitation of c-Fos+ and FosB+ neurons in chronic stress-exposed mice revealed that chronic activation of SST neurons leads to a paradoxical increase in pyramidal cell activity. Collectively, these data demonstrate that GABAergic microcircuits driven by dendrite targeting interneurons enable sex- and brain-region-specific neural plasticity that promotes stress resilience and reverses stress-induced anxiety- and anhedonia-like motivated behavior. Our studies provide a mechanistic rationale for antidepressant efficacy of dendrite-targeting, low-potency GABAA receptor agonists, independent of sex and despite striking sex differences in the relevant brain substrates.

neuroscience↗

bioRxiv2023

Sequential deregulation of histone marks, chromatin accessibility and gene expression in response to PROTAC-induced degradation of ASH2L

The trithorax protein ASH2L is essential for organismal and tissue development. As a subunit of COMPASS/KMT2 complexes, ASH2L is necessary for methylation of histone H3 lysine 4 (H3K4). Mono- and trimethylation at this site mark active enhancers and promoters, respectively, although the molecular relevance of H3K4 methylation is only partially understood. Due to the importance of ASH2L in all 6 COMPASS-like complexes and its long half-life, it has been difficult to define direct consequences. To overcome this limitation, we employed a PROTAC system, which allows the rapid degradation of ASH2L and addressing direct effects. Loss of ASH2L resulted in rapid inhibition of proliferation of mouse embryo fibroblasts. Shortly after ASH2L degradation, H3K4me3 decreased with its half-life revealing considerable variability between promoters. Subsequently, H3K4me1 increased at promoters and decreased at some enhancers. H3K27ac and H3K27me3, histone marks closely linked to H3K4 methylation, were affected with considerable delay. In parallel, chromatin compaction increased at promoters. Of note, nascent gene transcription was not affected early but overall RNA expression was deregulated late after ASH2L loss. Together, these findings suggest that downstream effects are ordered but relatively slow, despite the rapid loss of ASH2L and inactivation of KMT2 complexes. It appears that the systems that control gene transcription are well buffered and strong effects are only beginning to unfold after considerable delay.

molecular biology↗

bioRxiv2022

Induction of senescence upon loss of the Ash2l core subunit of H3K4 methyltransferase complexes

Gene expression is controlled in part by post-translational modifications of core histones. Methylation of lysine 4 of histone H3 (H3K4), associated with open chromatin and gene transcription, is catalyzed by type 2 lysine methyltransferase complexes that require WDR5, RBBP5, ASH2L and DPY30 as core subunits. Ash2l is essential during embryogenesis and for maintaining adult tissues. To expand on the mechanistic understanding of Ash2l, we generated mouse embryo fibroblasts (MEFs) with conditional Ash2l alleles. Upon loss of Ash2l, methylation of H3K4 and gene expression were downregulated, which correlated with inhibition of proliferation and cell cycle progression. Moreover, we observed induction of senescence concomitant with a set of downregulated signature genes but independent of SASP. Many of the signature genes are FoxM1 responsive. Indeed, exogenous FOXM1 was sufficient to delay senescence. Thus, although the loss of Ash2l in MEFs has broad and complex consequences, a distinct set of downregulated genes promotes senescence.

cell biology↗