The strand exchange domain of tumor suppressor PALB2 is intrinsically disordered and promotes oligomerization-dependent DNA compaction
Kyriukha Y, Watkins MB, Redington JM, Chintalapati N, Ganti A, Dastvan R, Uversky VN, Hopkins JB, Pozzi N and Korolev S
The strand exchange domain of tumor suppressor PALB2 is intrinsically disordered and promotes oligomerization-dependent DNA compaction
Kyriukha Y, Watkins MB, Redington JM, Chintalapati N, Ganti A, Dastvan R, Uversky VN, Hopkins JB, Pozzi N and Korolev S
The partner and localizer of BRCA2 (PALB2) is a scaffold protein linking BRCA1 with BRCA2 and RAD51 during homologous recombination (HR). PALB2 interaction with DNA strongly enhances HR in cells, while the PALB2 DNA-binding domain (PALB2-DBD) supports DNA strand exchange . We determined that PALB2-DBD is intrinsically disordered beyond a single N-terminal α-helix. Coiled-coil mediated dimerization is stabilized by interaction between intrinsically disordered regions (IDRs) leading to a 2-fold structural compaction. Single-stranded (ss)DNA binding promotes additional structural compaction and protein tetramerization. Using confocal single-molecule FRET, we observed bimodal and oligomerization-dependent compaction of ssDNA bound to PALB2-DBD, suggesting a novel strand exchange mechanism. Bioinformatics analysis and preliminary observations indicate that PALB2 forms protein-nucleic acids condensates. Intrinsically disordered DBDs are prevalent in the human proteome. PALB2-DBD and similar IDRs may use a chaperone-like mechanism to aid formation and resolution of DNA and RNA multichain intermediates during DNA replication, repair and recombination.
SIX transcription factors are necessary for the activation of DUX4 expression in facioscapulohumeral muscular dystrophy
Fox A, Oliva J, Vangipurapu R and Sverdrup FM
SIX transcription factors are necessary for the activation of DUX4 expression in facioscapulohumeral muscular dystrophy
Fox A, Oliva J, Vangipurapu R and Sverdrup FM
Facioscapulohumeral muscular dystrophy (FSHD) is a common and progressive muscle wasting disease that is characterized by muscle weakness often first noticed in the face, the shoulder girdle and upper arms before progressing to the lower limb muscles. FSHD is caused by the misexpression of the Double Homeobox 4 (DUX4) transcription factor in skeletal muscle. While epigenetic derepression of D4Z4 macrosatellite repeats underlies DUX4 misexpression, our understanding of the complex transcriptional activation of DUX4 is incomplete.
Dietary fructose enhances tumour growth indirectly via interorgan lipid transfer
Fowle-Grider R, Rowles JL, Shen I, Wang Y, Schwaiger-Haber M, Dunham AJ, Jayachandran K, Inkman M, Zahner M, Naser FJ, Jackstadt MM, Spalding JL, Chiang S, McCommis KS, Dolle RE, Kramer ET, Zimmerman SM, Souroullas GP, Finck BN, Shriver LP, Kaufman CK, Schwarz JK, Zhang J and Patti GJ
Dietary fructose enhances tumour growth indirectly via interorgan lipid transfer
Fowle-Grider R, Rowles JL, Shen I, Wang Y, Schwaiger-Haber M, Dunham AJ, Jayachandran K, Inkman M, Zahner M, Naser FJ, Jackstadt MM, Spalding JL, Chiang S, McCommis KS, Dolle RE, Kramer ET, Zimmerman SM, Souroullas GP, Finck BN, Shriver LP, Kaufman CK, Schwarz JK, Zhang J and Patti GJ
Fructose consumption has increased considerably over the past five decades, largely due to the widespread use of high-fructose corn syrup as a sweetener. It has been proposed that fructose promotes the growth of some tumours directly by serving as a fuel. Here we show that fructose supplementation enhances tumour growth in animal models of melanoma, breast cancer and cervical cancer without causing weight gain or insulin resistance. The cancer cells themselves were unable to use fructose readily as a nutrient because they did not express ketohexokinase-C (KHK-C). Primary hepatocytes did express KHK-C, resulting in fructolysis and the excretion of a variety of lipid species, including lysophosphatidylcholines (LPCs). In co-culture experiments, hepatocyte-derived LPCs were consumed by cancer cells and used to generate phosphatidylcholines, the major phospholipid of cell membranes. In vivo, supplementation with high-fructose corn syrup increased several LPC species by more than sevenfold in the serum. Administration of LPCs to mice was sufficient to increase tumour growth. Pharmacological inhibition of ketohexokinase had no direct effect on cancer cells, but it decreased circulating LPC levels and prevented fructose-mediated tumour growth in vivo. These findings reveal that fructose supplementation increases circulating nutrients such as LPCs, which can enhance tumour growth through a cell non-autonomous mechanism.
Chromosome-level subgenome-aware de novo assembly provides insight into genome divergence after hybridization
Gardner C, Chen J, Hadfield C, Lu Z, Debruin D, Zhan Y, Donlin MJ, Ahn TH and Lin Z
Chromosome-level subgenome-aware de novo assembly provides insight into genome divergence after hybridization
Gardner C, Chen J, Hadfield C, Lu Z, Debruin D, Zhan Y, Donlin MJ, Ahn TH and Lin Z
Interspecies hybridization is prevalent in various eukaryotic lineages and plays important roles in phenotypic diversification, adaptation, and speciation. To better understand the changes that occurred in the different subgenomes of a hybrid species and how they facilitate adaptation, we have completed chromosome-level de novo assemblies of all chromosomes for a recently formed hybrid yeast, strain CBS380, using Oxford Nanopore Technologies' MinION long-read sequencing. We characterize the genome and compare it with its parent species, and , and other genomes to better understand genome evolution after a relatively recent hybridization event. We observe multiple recombination events between the subgenomes in each chromosome, followed by loss of heterozygosity (LOH) in nine chromosome pairs. In addition to maintaining nearly all gene content and synteny from its parental genomes, has acquired many genes from other yeast species, primarily through the introgression of , such as those involved in the maltose metabolism. Finally, the patterns of recombination and LOH suggest an allotetraploid origin of The gene acquisition and rapid LOH in the hybrid genome probably facilitated its adaptation to maltose brewing environments and mitigated the maladaptive effect of hybridization. This paper describes the first in-depth study using long-read sequencing technology of an hybrid genome, which may serve as an excellent reference for future studies of this important yeast and other yeast strains.
Human hnRNPA1 reorganizes telomere-bound replication protein A
Granger SL, Sharma R, Kaushik V, Razzaghi M, Honda M, Gaur P, Bhat DS, Labenz SM, Heinen JE, Williams BA, Tabei SMA, Wlodarski MW, Antony E and Spies M
Human hnRNPA1 reorganizes telomere-bound replication protein A
Granger SL, Sharma R, Kaushik V, Razzaghi M, Honda M, Gaur P, Bhat DS, Labenz SM, Heinen JE, Williams BA, Tabei SMA, Wlodarski MW, Antony E and Spies M
Human replication protein A (RPA) is a heterotrimeric ssDNA binding protein responsible for many aspects of cellular DNA metabolism. Dynamic interactions of the four RPA DNA binding domains (DBDs) with DNA control replacement of RPA by downstream proteins in various cellular metabolic pathways. RPA plays several important functions at telomeres where it binds to and melts telomeric G-quadruplexes, non-canonical DNA structures formed at the G-rich telomeric ssDNA overhangs. Here, we combine single-molecule total internal reflection fluorescence microscopy (smTIRFM) and mass photometry (MP) with biophysical and biochemical analyses to demonstrate that heterogeneous nuclear ribonucleoprotein A1 (hnRNPA1) specifically remodels RPA bound to telomeric ssDNA by dampening the RPA configurational dynamics and forming a ternary complex. Uniquely, among hnRNPA1 target RNAs, telomeric repeat-containing RNA (TERRA) is selectively capable of releasing hnRNPA1 from the RPA-telomeric DNA complex. We speculate that this telomere specific RPA-DNA-hnRNPA1 complex is an important structure in telomere protection.
Temporal variation in p38-mediated regulation of DUX4 in facioscapulohumeral muscular dystrophy
Vangipurapu R, Oliva J, Fox A and Sverdrup FM
Temporal variation in p38-mediated regulation of DUX4 in facioscapulohumeral muscular dystrophy
Vangipurapu R, Oliva J, Fox A and Sverdrup FM
Facioscapulohumeral muscular dystrophy (FSHD) is a degenerative muscle disease caused by loss of epigenetic silencing and ectopic reactivation of the embryonic double homeobox protein 4 gene (DUX4) in skeletal muscle. The p38 MAP kinase inhibitor losmapimod is currently being tested in FSHD clinical trials due to the finding that p38 inhibition suppresses DUX4 expression in preclinical models. However, the role of p38 in regulating DUX4 at different myogenic stages has not been investigated. We used genetic and pharmacologic tools in FSHD patient-derived myoblasts/myocytes to explore the temporal role of p38 in differentiation-induced DUX4 expression. Deletion of MAPK14/11 or inhibition of p38α/β caused a significant reduction in early differentiation-dependent increases in DUX4 and DUX4 target gene expression. However, in MAPK14/11 knockout cells, there remains a differentiation-associated increase in DUX4 and DUX4 target gene expression later in differentiation. Furthermore, pharmacologic inhibition of p38α/β only partially decreased DUX4 and DUX4 target gene expression in late differentiating myotubes. In xenograft studies, p38α/β inhibition by losmapimod failed to suppress DUX4 target gene expression in late FSHD xenografts. Our results show that while p38 is critical for DUX4 expression during early myogenesis, later in myogenesis a significant level of DUX4 expression is independent of p38α/β activity.
Membrane lipid nanodomains modulate HCN pacemaker channels in nociceptor DRG neurons
Handlin LJ, Macchi NL, Dumaire NLA, Salih L, Lessie EN, McCommis KS, Moutal A and Dai G
Membrane lipid nanodomains modulate HCN pacemaker channels in nociceptor DRG neurons
Handlin LJ, Macchi NL, Dumaire NLA, Salih L, Lessie EN, McCommis KS, Moutal A and Dai G
Cell membranes consist of heterogeneous lipid nanodomains that influence key cellular processes. Using FRET-based fluorescent assays and fluorescence lifetime imaging microscopy (FLIM), we find that the dimension of cholesterol-enriched ordered membrane domains (OMD) varies considerably, depending on specific cell types. Particularly, nociceptor dorsal root ganglion (DRG) neurons exhibit large OMDs. Disruption of OMDs potentiated action potential firing in nociceptor DRG neurons and facilitated the opening of native hyperpolarization-activated cyclic nucleotide-gated (HCN) pacemaker channels. This increased neuronal firing is partially due to an increased open probability and altered gating kinetics of HCN channels. The gating effect on HCN channels is likely due to a direct modulation of their voltage sensors by OMDs. In animal models of neuropathic pain, we observe reduced OMD size and a loss of HCN channel localization within OMDs. Additionally, cholesterol supplementation inhibited HCN channels and reduced neuronal hyperexcitability in pain models. These findings suggest that disturbances in lipid nanodomains play a critical role in regulating HCN channels within nociceptor DRG neurons, influencing pain modulation.
Seeding-competent TDP-43 persists in human patient and mouse muscle
Lynch EM, Pittman S, Daw J, Ikenaga C, Chen S, Dhavale DD, Jackrel ME, Ayala YM, Kotzbauer P, Ly CV, Pestronk A, Lloyd TE and Weihl CC
Seeding-competent TDP-43 persists in human patient and mouse muscle
Lynch EM, Pittman S, Daw J, Ikenaga C, Chen S, Dhavale DD, Jackrel ME, Ayala YM, Kotzbauer P, Ly CV, Pestronk A, Lloyd TE and Weihl CC
TAR DNA binding protein 43 (TDP-43) is an RNA binding protein that accumulates as aggregates in the central nervous systems of some patients with neurodegenerative diseases. However, TDP-43 aggregation is also a sensitive and specific pathologic feature found in a family of degenerative muscle diseases termed inclusion body myopathy. TDP-43 aggregates from amyotrophic lateral sclerosis (ALS) and frontotemporal dementia brain lysates may serve as self-templating aggregate seeds in vitro and in vivo, supporting a prion-like spread from cell to cell. Whether a similar process occurs in patient muscle is not clear. We developed a mouse model of inducible, muscle-specific cytoplasmic localized TDP-43. These mice develop muscle weakness with robust accumulation of insoluble and phosphorylated sarcoplasmic TDP-43, leading to eosinophilic inclusions, altered proteostasis, and changes in TDP-43-related RNA processing that resolve with the removal of doxycycline. Skeletal muscle lysates from these mice also have seeding-competent TDP-43, as determined by a FRET-based biosensor, that persists for weeks upon resolution of TDP-43 aggregate pathology. Human muscle biopsies with TDP-43 pathology also contain TDP-43 aggregate seeds. Using lysates from muscle biopsies of patients with sporadic inclusion body myositis (IBM), immune-mediated necrotizing myopathy (IMNM), and ALS, we found that TDP-43 seeding capacity was specific to IBM. TDP-43 seeding capacity anticorrelated with TDP-43 aggregate and vacuole abundance. These data support that TDP-43 aggregate seeds are present in IBM skeletal muscle and represent a unique TDP-43 pathogenic species not previously appreciated in human muscle disease.
Mechanistic basis of activation and inhibition of protein disulfide isomerase by allosteric antithrombotic compounds
Ponzar N, Chinnaraj M, Pagotto A, De Filippis V, Flaumenhaft R and Pozzi N
Mechanistic basis of activation and inhibition of protein disulfide isomerase by allosteric antithrombotic compounds
Ponzar N, Chinnaraj M, Pagotto A, De Filippis V, Flaumenhaft R and Pozzi N
Protein disulfide isomerase (PDI) is a promising target for combating thrombosis. Extensive research over the past decade has identified numerous PDI-targeting compounds. However, limited information exists regarding how these compounds control PDI activity, which complicates further development.
Etomoxir: an old dog with new tricks
McGuffee RM, McCommis KS and Ford DA
Etomoxir: an old dog with new tricks
McGuffee RM, McCommis KS and Ford DA