Redox priming promotes Aurora A activation during mitosis
Ontology highlight
ABSTRACT: Samples of Aurora A kinase domain were covalently labeled with disulfide-containing compounds and analyzed by mass spectrometry to determine the extent of covalent labeling.
Project description:Cell cycle-dependent redox changes can mediate transient covalent modifications of cysteine thiols to modulate the activities of regulatory kinases and phosphatases. Our previously reported finding that protein cysteine oxidation is increased during mitosis relative to other cell cycle phases suggests that redox modifications could play prominent roles in regulating mitotic processes. The Aurora family of kinases and their downstream targets are key components of the cellular machinery that ensures the proper execution of mitosis and the accurate segregation of chromosomes to daughter cells. In this study, x-ray crystal structures of the Aurora A kinase domain delineate redox-sensitive cysteine residues that, upon covalent modification, can allosterically regulate kinase activity and oligomerization state. We showed in both Xenopus laevis egg extracts and mammalian cells that a conserved cysteine residue within the Aurora A activation loop is crucial for Aurora A activation by autophosphorylation. We further showed that covalent disulfide adducts of this residue promote autophosphorylation of the Aurora A kinase domain. These findings reveal a potential mechanistic link between Aurora A activation and changes in the intracellular redox state during mitosis and provide insights into how novel small-molecule inhibitors may be developed to target specific subpopulations of Aurora A.
Project description:Pharmacological activation of the activating transcription factor 6 (ATF6) arm of the Unfolded Protein Response (UPR) has proven useful for ameliorating proteostasis deficiencies in a variety of etiologically diverse diseases. Previous high-throughput screening efforts identified the small molecule AA147 as a potent and selective ATF6 activating compound that operates through a mechanism involving metabolic activation of its 2-amino- p -cresol substructure affording a quinone methide, which then covalently modifies a subset of ER protein disulfide isomerases (PDIs). Intriguingly, another compound identified in this screen, AA132, also contains a 2-amino- p -cresol moiety; however, this compound showed less transcriptional selectivity, instead globally activating all three arms of the UPR. Here, we show that AA132 activates global UPR signaling through a mechanism analogous to that of AA147, involving metabolic activation and covalent PDI modification. Chemoproteomic-enabled analyses show that AA132 covalently modifies PDIs to a greater extent than AA147. Paradoxically, activated AA132 reacts slower with PDIs, indicating it is less reactive than activated AA147. This suggests that the higher labeling of PDIs observed with activated AA132 can be attributed to its lower reactivity, which allows this activated compound to persist longer in the cellular environment prior to quenching by endogenous nucleophiles. Collectively, these results suggest that AA132 globally activates the UPR through increased engagement of ER PDIs. Consistent with this, reducing the cellular concentration of AA132 decreases PDI modifications and allows for selective ATF6 activation. Our results highlight the relationship between metabolically activatable-electrophile stability, ER proteome reactivity, and the transcriptional response observed with the enaminone chemotype of ER proteostasis regulators, enabling continued development of next-generation ATF6 activating compounds.
Project description:<p>The redox state of proteins is essential for their function and guarantees cell fitness. Peroxiredoxins protect cells against oxidative stress, maintain redox homeostasis, act as chaperones, and transmit hydrogen peroxide signals to redox regulators. Despite the profound structural and functional knowledge of peroxiredoxins action, information on how the different functions are concerted is still scarce. Using global proteomic analyses, we show here that the yeast peroxiredoxin Tsa1 interacts with many proteins of essential biological processes, including protein turnover and carbohydrate metabolism. Several of these interactions are of a covalent nature, and we show that failure of peroxiredoxinylation of Gnd1 affects its phosphogluconate dehydrogenase activity and impairs recovery upon stress. Thioredoxins directly remove TSA1-formed mixed disulfide intermediates, thus expanding the role of the thioredoxin-peroxiredoxin redox cycle pair to buffer the redox state of proteins.</p>
Project description:Aurora B kinase, as part of the chromosomal passenger complex (CPC), controls key processes during the cell cycle such as DNA compaction, genome partitioning or cytokinesis. Nonetheless, increased Aurora B levels are a potential threat for the cells and have been linked to different tumor types. We have carried out an exhaustive characterization of the global consequences of the overexpression of Aurora B and INCENP, the scaffold of the CPC and an activator of Aurora B kinase activity, in non-transformed human cells. Our data demonstrate, not only that an individual increase in the levels of Aurora B or INCENP have a different impact on the cells, but more importantly that their simultaneous overexpression stabilizes both CPC components, exacerbates Aurora B activity, severely impairs mitotic progression and chromosome dynamics, and has a distinctive and more dramatic effect on the transcriptional landscape of the cells.
Project description:Aurora B kinase, as part of the chromosomal passenger complex (CPC), controls key processes during the cell cycle such as DNA compaction, genome partitioning or cytokinesis. Nonetheless, increased Aurora B levels are a potential threat for the cells and have been linked to different tumor types. We have carried out an exhaustive characterization of the global consequences of the overexpression of Aurora B and INCENP, the scaffold of the CPC and an activator of Aurora B kinase activity, in non-transformed human cells. Our data demonstrate, not only that an individual increase in the levels of Aurora B or INCENP have a different impact on the cells, but more importantly that their simultaneous overexpression stabilizes both CPC components, exacerbates Aurora B activity, severely impairs mitotic progression and chromosome dynamics, and has a distinctive and more dramatic effect on the transcriptional landscape of the cells.
Project description:The endoplasmic reticulum (ER) is the organelle of nucleated cells that produces lipids, sugars and proteins. More than 20 ER-resident members of the Protein Disulfide Isomerase (PDI) family regulate formation, isomerization and disassembly of covalent bonds in newly synthesized polypeptides. The PDI family includes few membrane-bound members. Among these, TMX1, TMX2, TMX3, TMX4 and TMX5 belong to the thioredoxin-related transmembrane (TMX) protein family. TMX5 is the least known member of the family. Here, we establish that TMX5 covalently engages via its active site cysteine residue at position 220 a subset of secretory proteins, mainly single- and multi-pass Golgi-resident polypeptides. TMX5 also interacts non-covalently, and covalently, via non-catalytic cysteine residues, with the PDI family members PDI, ERp57 and ERp44. The association of TMX5 and ERp44 requires formation of a mixed disulfide between the catalytic cysteine residue 29 of ERp44 and the non-catalytic cysteine residues 114 and/or 124 of TMX5 and controls the ER retention of TMX5. Thus, TMX5 belongs to the family of proteins including Ero1, Ero1, Prx4, ERAP1, SUMF1 that do not display ER retention sequences and rely on ERp44 engagement for proper inter-compartmental distribution. The client-specificity of TMX5 in cellulo was assessed by expressing mutant forms of the enzymes, where the last cysteine residue of the TMX’s CXXC catalytic sites has been mutated to alanine, which stabilizes the mixed disulfide that oxidoreductases establish with clients. Clients remain disulfide-bonded to the oxidoreductase and are identified upon co-immunoprecipitation and mass spectrometry analyses.
Project description:Poly(ADP-ribose) polymerases (PARP1 and PARP2) contribute to DNA base excision repair (BER) and DNA demethylation and has been implicated in epigenetic programming in early mammalian development. Recently, proteomic analyses identified BER proteins to be covalently poly-ADP-ribosylated by PARPs. The role of this posttranslational modification in the BER process is unknown. Here, we show that PARP1 senses AP-sites and SSBs generated during TET-TDG mediated active DNA demethylation and covalently attaches PAR to each BER protein engaged. Covalent PARylation dissociates BER proteins from DNA, which accelerates completion of the repair process. Consistently, inhibition of PARylation in mESC resulted both in reduced locus specific TET-TDG-targeted DNA demethylation, and in reduced general repair of random DNA damage. Our findings establish a critical function of covalent protein PARylation in coordinating molecular processes associated with dynamic DNA methylation.
Project description:We show that Aurora-B phosphorylates heterogeneous nuclear ribonucleoprotein U (hnRNP U) in the SAP domain to dissociate hnRNP U from chromatin during mitosis. We use RNA-seq to show that hnRNP U associates with hundreds of mRNAs and lncRNAs during interphase and mitosis.
Project description:Tether-seq uses s4U metabolic labeling to provide sites for reversible and covalent attachment of small molecule disulfides to the transcriptome. By screening under reducing conditions, we are able to highlight interactions that are stabilized by binding over those driven by the reactivity of the RNA sites. When applied to cellular RNA, Tether-seq with a disulfide analogue of risdiplam (compound 2) revealed a number of potential binding sites. Structure probing by SHAPE-MaP revealed a structured motif and confirmed binding to the lead molecule.
Project description:By arresting tumor cells in mitosis, aurora A kinase inhibition restores interferon signaling in small cell lung cancer tumor cells and cooperates with PD-L1 immune checkpoint blockade.