Biology subjects

Watts, J.

Publications and source records attributed to Watts, J..

5 recordsLinked to original sources

bioRxiv2023

Upregulated pexophagy limits the capacity of selective autophagy

Selective autophagy is an essential mechanism to maintain organelle integrity and cellular homeostasis through the constant recycling of damaged or superfluous components. While distinct selective autophagy pathways mediate the degradation of diverse cellular substrates including organelles and pathogens, whether these distinct pathways can influence one another remains unknown. We address this question here using pexophagy, the autophagic degradation of peroxisomes, as a model. We demonstrate in cells that upregulated pexophagy exhausts selective autophagy and limits the degradation of both mitochondria and protein aggregates. We confirmed this finding in the pexophagy-mediated form of Zellweger Spectrum Disorder, a rare disease characterized by peroxisome dysfunction. Further, we extend the generalizability of limited selective autophagy by determining that increased aggrephagy reduces pexophagy using a model of Huntingtons Disease. Our findings suggest that the degradative capacity of selective autophagy can become limited by an increased substrate load.

cell biology↗

bioRxiv2023

Nuclear receptor signaling via NHR-49/MDT-15 regulates stress resilience and proteostasis in response to reproductive and metabolic cues

The ability to sense and respond to proteotoxic insults declines with age, leaving cells vulnerable to chronic and acute stressors. Reproductive cues modulate this decline in cellular proteostasis to influence organismal stress resilience in C. elegans. We previously uncovered a pathway that links the integrity of developing embryos to somatic health in reproductive adults. Here, we show that the nuclear receptor NHR-49, a functional homolog of mammalian peroxisome proliferator-activated receptor alpha (PPAR), regulates stress resilience and proteostasis downstream of embryo integrity and other pathways that influence lipid homeostasis, and upstream of HSF-1. Disruption of the vitelline layer of the embryo envelope, which activates a proteostasis-enhancing inter-tissue pathway in somatic tissues, also triggers changes in lipid catabolism gene expression that are accompanied by an increase in fat stores. NHR-49 together with its co-activator MDT-15 contributes to this remodeling of lipid metabolism and is also important for the elevated stress resilience mediated by inhibition of the embryonic vitelline layer as well as by other pathways known to change lipid homeostasis, including reduced insulin-like signaling and fasting. Further, we show that increased NHR-49 activity is sufficient to suppress polyglutamine aggregation and improve stress resilience in an HSF-1-dependent manner. Together, our results establish NHR-49 as a key regulator that links lipid homeostasis and cellular resilience to proteotoxic stress.

genetics↗

bioRxiv2022

Formamide significantly enhances the efficiency of chemical adenylation of RNA sequencing ligation adaptors

Pre-adenylated single-stranded DNA ligation adaptors are essential reagents in many next generation RNA sequencing library preparation protocols. These oligonucleotides can be adenylated enzymatically or chemically. Enzymatic adenylation reactions have high yield but are not amendable to scale up. In chemical adenylation, Adenosine 5{square}-phosphorimidazolide (ImpA) reacts with 5' phosphorylated DNA. It is easily scalable but gives poor yields, requiring labor-intensive cleanup steps. Here, we describe an improved chemical adenylation method using 95% formamide as the solvent, which results in the adenylation of oligonucleotides with >90% yield. In standard conditions, with water as the solvent, hydrolysis of the starting material to adenosine monophosphate limits the yields. To our surprise, we find that rather than increasing adenylation yields by decreasing the rate of ImpA hydrolysis, formamide does so by increasing the reaction rate between ImpA and 5'-phosphorylated DNA by [~]10 fold. The method described here enables straightforward preparation of chemically adenylated adapters with higher than 90% yield, simplifying reagent preparation for NGS.

molecular biology↗

bioRxiv2022

Structure of the catalytically active APOBEC3G bound to a DNA oligonucleotide inhibitor reveals tetrahedral geometry of the transition state

APOBEC3 proteins (A3s) are enzymes that catalyze deamination of cytidine to uridine in single-stranded DNA (ssDNA) substrates, thus playing a key role in innate antiviral immunity. However, APOBEC3 family has also been linked to many mutational signatures in cancer cells, which has led to intense interest to develop inhibitors of A3s catalytic activity as therapeutics as well as tools to study A3s biochemistry, structure and cellular function. Recent studies have shown that ssDNA containing 2'-deoxy-zebularine (dZ-ssDNA) is an inhibitor of A3s such as A3A, A3B and A3G, although atomic determinants of this activity remained unknown. To fill this knowledge gap, we determined a 1.5 [A] resolution structure of a dZ-ssDNA inhibitor bound to active A3G. The crystal structure revealed that the activated dZ/H2O mimics the transition state by coordinating the active site Zn2+ and engaging in additional stabilizing interactions, such as the one with the catalytic residues E259. Therefore, this structure allowed us to capture the first snapshot of the A3s transition state, and suggests that developing transition-state mimicking inhibitors may provide a new opportunity to design more targeted molecules for A3s in the future.

biochemistry↗

bioRxiv2022

Chemotherapy Signatures Map Evolution of Therapy-Related Myeloid Neoplasms

Patients treated with cytotoxic therapies, including autologous stem cell transplantation, are at risk for developing therapy-related myeloid neoplasms1, 2. Pre-leukemic clones (i.e., clonal hematopoiesis) are detectable years before the development of these aggressive malignancies3-5, though the genomic events leading to transformation and expansion are not well-defined. Here, leveraging distinctive chemotherapy-associated mutational signatures6-12 from whole-genome sequencing data and targeted sequencing of pre-chemotherapy samples, we reconstruct the evolutionary life-history of 39 therapy-related myeloid malignancies. A dichotomy is revealed, in which neoplasms with evidence of chemotherapy-induced mutagenesis from platinum and melphalan are relatively hypermutated and enriched for complex structural variants (i.e., chromothripsis), while neoplasms with alternative exposures bear a similar profile to de novo acute myeloid leukemia. Using chemotherapy-associated mutational signatures as a temporal barcode in each patients life, we estimate that several complex events and genomic drivers are acquired after chemotherapy exposure. In the case of treatment with high-dose melphalan and autologous stem cell transplantation, we demonstrate that the procedure allows clonal hematopoiesis to escape chemotherapy exposure entirely, and to be reinfused to expand to malignancy. This information reveals a novel mode of malignant progression for therapy-related malignancies that is not reliant on direct mutagenesis or even exposure to chemotherapy, itself, and prompts further investigation into leukemia-permissive effects of cytotoxic drugs.

cancer biology↗