Biology subjects

Scalf, M.

Publications and source records attributed to Scalf, M..

9 recordsLinked to original sources

bioRxiv2025

Cholinergic regulation of prolonged alcohol withdrawal differs by sex

Acute alcohol withdrawal encompasses somatic withdrawal signs and increased negative affect. In prolonged alcohol withdrawal the somatic withdrawal signs have resolved but the increased negative affect persists. We investigated acute and prolonged alcohol withdrawal after 9 daily injections of 2.5 g/kg alcohol plus 4-methypyrazole, an alcohol dehydrogenase inhibitor, in male and female C57BL/6J mice, and examined whether nicotinic acetylcholine receptor (nAChR) drugs could attenuate withdrawal-induced negative affect. Male mice showed changing somatic withdrawal signs over time and negative affect that persisted at least 21 days into withdrawal. Pre-treatment with mecamylamine, a non-specific nAChR antagonist, or varenicline, a nAChR partial agonist, reduced withdrawal-induced anxiety- and compulsive-like behavior in the marble-burying test during prolonged withdrawal. In contrast, female mice did not exhibit somatic withdrawal signs or anxiety- or compulsive-like behaviors. Instead, female mice showed a deficit in social interaction that was not attenuated by mecamylamine. Alcohol clearance and sedation were not different between sexes, indicating that differences in withdrawal signs and negative affect are not confounded by differences in alcohol metabolism. These findings suggest that cholinergic drugs may be a promising therapeutic for withdrawal-induced negative affect in male, but not female, mice.

pharmacology and toxicology↗

bioRxiv2025

Interactome screening implicates BAG6 as a suppressor of UBQLN2 misfolding in ALS-dementia

Ubiquilin-2 (UBQLN2) is a ubiquitin (Ub)-binding shuttle protein that is mutated in X-linked forms of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). ALS/FTD-linked mutations in UBQLN2 disrupt its conformation, increasing its tendency to form cytoplasmic aggregates that may disrupt cellular regulation through loss-of-function (LOF) and gain-of-function (GOF) effects. To explore how ALS-associated mutations impact UBQLN2 function, we performed quantitative mass spectrometry (MS)-based interactome analysis using affinity-purified UBQLN2 from inducible pluripotent stem cells (iPSCs) and induced motor neurons (iMNs) expressing wild-type UBQLN2 (UBQLN2WT), a UBQLN2P497H clinical mutant, or a UBQLN24XALS allele harboring four disease mutations. Proteins showing enhanced association with ALS-mutant UBQLN2 proteins included PEG10, a known degradation target of UBQLN2, and BAG6, a chaperone involved in the triage of mislocalized proteins (MLPs). BAG6 knockdown inhibited the solubility recovery of both wild-type and ALS-mutant UBQLN2 proteins following heat stress (HS), suggesting it functions as a UBQLN2 holdase. In addition, knockdown of BAG6 or knockout of UBQLN2 led to PEG10 accumulation, implicating both in PEG10 turnover; however, neither BAG6 nor UBQLN2 was required for PEG10 degradation in response to HS. The aggregation prone UBQLN24XALS mutant showed increased PEG10 binding and modestly delayed PEG10 turnover while PEG10 degradation was not significantly different between UBQLN2WT and UBQLN2P497H iPSCs. The combined findings implicate BAG6 a UBQLN2 holdase and identify a suite of proteins whose altered binding may contribute to pathologic changes in UBQLN2-associated ALS/FTD.

molecular biology↗

bioRxiv2024

Alternative splicing modulates chromatin interactome and phase separation of the RIF1 C-terminal domain

How RIF1 (RAP1 interacting factor) fulfills its diverse roles in DNA double-strand break (DSB) repair, DNA replication, and nuclear organization remains elusive. Here we show that alternative splicing (AS) of a cassette exon (Ex32) encoding a Ser/Lys-rich (S/K) cassette in the RIF1 C-terminal domain (CTD) gives rise to RIF1-Long (RIF1-L) and RIF1-Short (RIF1-S) isoforms with different functional characteristics. We demonstrate that RIF1-Ex32 splice-in is mediated by an exonic splicing enhancer that is recognized by the splicing factor SRSF1 and antagonized by splicing inhibitors SRSF3 and SRSF7. Exposure to DNA damage inhibited Ex32 splice-in, potentiated the association of SRSF3 and SRSF7 with RIF1 pre-mRNA, and caused an increase in RIF1-S protein expression, which was also observed across a diverse set of primary cancers. Isoform-specific proteomic analyses revealed RIF1-L preferentially associated with mediator of DNA damage checkpoint 1 (MDC1) and sustained MDC1 focus formation to a greater extent than RIF1-S. We further show that the S/K cassette stabilized a novel phase separation activity of the RIF1 CTD and enhanced RIF1-L chromatin retention, which was reversed by CDK1-dependent phosphorylation of the RIF1 CTD in response to G2 DNA damage checkpoint inhibition. These combined findings suggest DNA damage-dependent RIF1 AS contributes to RIF1 functional diversification in genome protection.

molecular biology↗

bioRxiv2024

Discovery of dehydroamino acids and their crosslinks in Tau and other aggregating proteins of Alzheimers disease

BackgroundAlzheimers disease (AD) is characterized by accumulation of two types of protein aggregates, senile plaques and neurofibrillary tangles, which strongly contribute to the pathogenesis of the disease. Senile plaques consist primarily of aggregated amyloid-{beta}, while neurofibrillary tangles form via aggregation of the protein Tau, as well as other microtubule-associated proteins such as CRMP2. Posttranslational modifications have been hypothesized to contribute to the initial aggregation events that lead to SPs and NFTs. Dehydroamino acids (DHAAs) are posttranslational modifications rarely observed in humans and have not previously been reported in AD. DHAAs arise from the eliminylation of serine, threonine, or cysteine, yielding a double bond with distinct molecular geometry and reactivity. Their geometry can produce secondary structure rearrangements, such as those seen in senile plaque and neurofibrillary tangle formation, while their reactivity can cause intramolecular or intermolecular (protein-protein) crosslinking. We hypothesized that this modification might be present in protein aggregation-associated neurodegenerative disorders like AD. MethodsWe performed mass spectrometry-based bottom-up proteomics on the sarkosyl-insoluble (protein aggregate-enriched) material from ten AD brains and three age-matched controls. Identifications of DHAA-mediated crosslinked peptides were validated using both an isotopic labeling strategy and spike-in experiments employing synthetic crosslinked peptide standards. Similar findings were obtained in searches of publicly available proteomic datasets from AD and control brains. ResultsWe identified 412 sites of DHAA modification in 184 proteins, with the highest prevalence in the neurofibrillary tangle-forming proteins Tau and CRMP2. Comparison with results of previous protein aggregate interactomics studies show that proteins containing the DHAA modification are more highly associated with protein aggregates than are proteins containing any other individual posttranslational modification. We further observed 11 protein crosslinks arising from DHAAs, including three from the Tau protein. Label free quantification showed that Tau crosslinks are an order of magnitude more prevalent in AD samples than in age-matched controls. ConclusionsDehydroamino acids and their derivatives are prevalent modifications in the Alzheimers disease brain proteome. These modifications give rise to protein crosslinks which may contribute to protein aggregation processes.

biochemistry↗

bioRxiv2023

Defining distinct RNA-protein interactomes of SARS-CoV-2 genomic and subgenomic RNAs

Host RNA binding proteins recognize viral RNA and play key roles in virus replication and antiviral defense mechanisms. SARS-CoV-2 generates a series of tiered subgenomic RNAs (sgRNAs), each encoding distinct viral protein(s) that regulate different aspects of viral replication. Here, for the first time, we demonstrate the successful isolation of SARS-CoV-2 genomic RNA and three distinct sgRNAs (N, S, and ORF8) from a single population of infected cells and characterize their protein interactomes. Over 500 protein interactors (including 260 previously unknown) were identified as associated with one or more target RNA at either of two time points. These included protein interactors unique to a single RNA pool and others present in multiple pools, highlighting our ability to discriminate between distinct viral RNA interactomes despite high sequence similarity. The interactomes indicated viral associations with cell response pathways including regulation of cytoplasmic ribonucleoprotein granules and posttranscriptional gene silencing. We validated the significance of five protein interactors predicted to exhibit antiviral activity (APOBEC3F, TRIM71, PPP1CC, LIN28B, and MSI2) using siRNA knockdowns, with each knockdown yielding increases in viral production. This study describes new technology for studying SARS-CoV-2 and reveals a wealth of new viral RNA-associated host factors of potential functional significance to infection.

molecular biology↗

bioRxiv2022

Axon guidance pathways modulate neurotoxicity of ALS-associated UBQLN2

Mutations in the ubiquitin (Ub) chaperone Ubiquilin 2 (UBQLN2) cause X-linked forms of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) through unknown mechanisms. Here we show that aggregation-prone, ALS-associated mutants of UBQLN2 (UBQLN2ALS) trigger heat stress-dependent neurodegeneration in Drosophila. A genetic modifier screen implicated endolysosomal and axon guidance genes, including the netrin receptor, Unc-5, as key modulators of UBQLN2 toxicity. Reduced gene dosage of Unc-5 or its coreceptor Dcc/frazzled diminished neurodegenerative phenotypes, including motor dysfunction, neuromuscular junction defects, and shortened lifespan, in flies expressing UBQLN2ALS alleles. Induced pluripotent stem cells (iPSCs) harboring UBQLN2ALS knockin mutations exhibited lysosomal defects while inducible motor neurons (iMNs) expressing UBQLN2ALS alleles exhibited cytosolic UBQLN2 inclusions, reduced neurite complexity, and growth cone defects that were partially reversed by silencing of UNC5B and DCC. The combined findings suggest that altered growth cone dynamics are a conserved pathomechanism in UBQLN2-associated ALS/FTD.

neuroscience↗

bioRxiv2021

Multi-Factor Authentication of Potential 5' Splice Sites by the Saccharomyces cerevisiae U1 snRNP

In eukaryotes, splice sites define the introns of pre-mRNAs and must be recognized and excised with nucleotide precision by the spliceosome to make the correct mRNA product. In one of the earliest steps of spliceosome assembly, the U1 small nuclear ribonucleoprotein (snRNP) recognizes the 5 splice site (5 SS) through a combination of base pairing, protein-RNA contacts, and interactions with other splicing factors. Previous studies investigating the mechanisms of 5 SS recognition have largely been done in vivo or in cellular extracts where the U1/5 SS interaction is difficult to deconvolute from the effects of trans-acting factors or RNA structure. In this work we used co-localization single-molecule spectroscopy (CoSMoS) to elucidate the pathway of 5 SS selection by purified yeast U1 snRNP. We determined that U1 reversibly selects 5 SS in a sequence-dependent, two-step mechanism. A kinetic selection scheme enforces pairing at particular positions rather than overall duplex stability to achieve long-lived U1 binding. Our results provide a kinetic basis for how U1 may rapidly surveil nascent transcripts for 5 SS and preferentially accumulate at these sequences rather than on close cognates. IMPACT STATEMENTThe yeast U1 snRNP recognizes multiple features of target RNAs to reversibly identify splicing-competent 5 splice sites.

biochemistry↗

bioRxiv2020

Identifying HIV-1 RNA splice variant protein interactomes using HyPR-MSSV

HIV-1 generates unspliced (US), partially spliced (PS), and completely spliced (CS) classes of RNAs; each playing distinct roles in viral replication. Elucidating their host protein "interactomes" is crucial to understanding virus-host interplay. Here, we present HyPR-MSSV for isolation of US, PS, and CS transcripts from a single population of infected CD4+ T-cells and mass spectrometric identification of their in vivo protein interactomes. Analysis revealed 212 proteins differentially associated with the unique RNA classes; including, preferential association of regulators of RNA stability with US- and PS-transcripts and, unexpectedly, mitochondria-linked proteins with US-transcripts. Remarkably, >80 of these factors screened by siRNA knock-down impacted HIV-1 gene expression. Fluorescence microscopy confirmed several to co-localize with HIV-1 US RNA and exhibit changes in abundance and/or localization over the course of infection. This study validates HyPR-MSSV for discovery of viral splice variant protein interactomes and provides an unprecedented resource of factors and pathways likely important to HIV-1 replication.

biochemistry↗

bioRxiv2020

Fused in sarcoma regulates DNA replication timing and progression

Fused in sarcoma (FUS) encodes a low complexity RNA-binding protein with diverse roles in transcriptional activation and RNA processing. While oncogenic fusions of FUS and transcription factor DNA-binding domains are associated with soft tissue sarcomas, dominant mutations in FUS cause amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). FUS has also been implicated in DNA double-strand break repair (DSBR) and genome maintenance. However, the underlying mechanisms are unknown. Here we employed quantitative proteomics, transcriptomics, and DNA copy number analysis (Sort-Seq), in conjunction with FUS-/- cells to ascertain roles of FUS in genome protection. FUS-/- cells exhibited alterations in the recruitment and retention of DSBR factors BRCA1 and 53BP1 but were not overtly sensitive to genotoxins. By contrast, FUS-deficient cells had reduced proliferative potential that correlated with reduced replication fork speed, diminished loading of pre-replication complexes, and attenuated expression of S-phase associated genes. FUS interacted with lagging strand DNA synthesis factors and other replisome components, but did not translocate with active replication forks. Using a Sort-Seq workflow, we show that FUS contributes to genome-wide control of DNA replication timing and is essential for the early replication of transcriptionally active DNA. These findings illuminate new roles for FUS in DNA replication initiation and timing that may contribute to genome instability and functional defects in cells harboring disease-associated FUS fusions.

genomics↗