Project description:Structural maintenance of chromosomes (SMC) complexes, cohesin, condensin and Smc5/6, are essential for viability and participate in multiple processes, including sister chromatid cohesion, chromosome condensation, and DNA repair. Here we show that SUMO chains target all three SMC complexes and are antagonized by the SUMO protease Ulp2 to prevent their turnover. We uncover that the essential role of the cohesin-associated subunit Pds5 is to counteract SUMO chains jointly with Ulp2. Importantly, fusion of Ulp2 to kleisin Scc1 supports viability of PDS5 null cells and protects cohesin from proteasomal degradation mediated by the SUMO-targeted ubiquitin ligase Slx5/Slx8. The lethality of PDS5 deleted cells can also be bypassed by simultaneous loss of the PCNA unloader, Elg1, and the cohesin releaser, Wpl1, but only when Ulp2 is functional. Condensin and Smc5/6 complex are similarly guarded by Ulp2 against unscheduled SUMO-chain assembly, which we propose to time the availability of SMC complexes on chromatin.
Project description:A SILAC-based quantitative affinity purification experiment was performed to study the protein binders of the N-terminal region (1-310) of PRPF40A and its mutated version with the proline-rich sequence substituted by a polyalanine stretch.
Project description:Many soluble proteins interact with membranes to perform important biological functions, including signal transduction, regulation, transport, trafficking and biogenesis. Despite their importance, these protein-membrane interactions are difficult to characterize due to their often-transient nature as well as phospholipids’ poor solubility in aqueous solution. Here, we employ nanodiscs – small, water-soluble patches of lipid bilayer encircled with amphipathic scaffold proteins – along with quantitative proteomics to identify lipid-binding proteins in S. cerevisiae. Using nanodiscs reconstituted with yeast total lipid extracts or only phosphatidylethanolamine (PE-nanodiscs), we capture several known membrane-interacting proteins, including the Rab GTPases Sec4 and Ypt1, which play key roles in vesicle trafficking. Utilizing PE-nanodiscs enriched with phosphatidic acid (PEPA-nanodiscs), we specifically capture a member of the Hsp40/J-protein family, Caj1, whose function has recently been linked to membrane protein quality control. We show that Caj1 interaction with liposomes containing PA is modulated by pH and PE lipids, and depends on two patches of positively charged residues near the C-terminus of the protein. The protein Caj1 is the first example of an Hsp40/J-domain protein with affinity for membranes and phosphatidic acid lipid specificity. These findings highlight the utility of the nanodisc system to identify and characterize protein-lipid interactions that may not be evident using other methods.
Project description:Protein expression is regulated by production and degradation of mRNAs and proteins, but their specific relationships remain unknown. We combine measurements of protein production and degradation and mRNA dynamics to build a quantitative genomic model of the differential regulation of gene expression in LPS stimulated mouse dendritic cells. Changes in mRNA abundance play a dominant role in determining most dynamic fold changes in protein levels. Conversely, the preexisting proteome of proteins performing basic cellular functions is remodeled primarily through changes in protein production or degradation, accounting for over half of the absolute change in protein molecules in the cell. Thus, the proteome is regulated by transcriptional induction of novel cellular functions and remodeling of preexisting functions through the protein life cycle. Mouse primary dendritic cells were treated with LPS or mock stimulus and profiled over a 12-hour time course. Cells were grown in M-labeled SILAC media, which was replaced with H-labeled SILAC media at time 0. Aliquots were taken at 0, 0.5, 1, 2, 3, 4, 5, 6, 9, and 12 hours post-stimulation and added to equal volumes of a master mix of unlabeled (L) cells for the purpose of normalization. RNA-Seq was performed at 0, 1, 2, 4, 6, 9, and 12 hours post-stimulation.
Project description:The H1069Q substitution in the liver-specific copper transporter ATP7B represents the major cause of Wilson disease. The mutated ATP7B undergoes rapid degradation in the endoplasmic reticulum (ER) and fails to reach copper excretion compartments thus causing severe copper toxicosis in patients. Modulating the ATP7B-H1069Q interactome was proposed as a rescue strategy but specific binding partners that might be targeted for mutant correction remain elusive. Here we try to identify a mutant-specific interactor for the pharmacological rescue of ATP7B-H1069Q.
Project description:Leishmania donovani, an intracellular protozoan parasite, is the causative agent of visceral leishmaniasis or kala-azar, the most severe form of leishmaniasis in humans. To date, our understanding of the molecular mechanisms associated with the pathogenicity of Leishmania infection is still limited. RNA interference—collectively RNA silencing pathways—participates in the regulation of various biological processes in most eukaryotic cells. Complexes of Argonaute proteins with small RNAs are core components of the RNA interference system and play a key role in silencing gene expression. It is becoming increasingly clear that several intracellular pathogens target host cell RNA interference pathways to promote their survival. In this study, we investigated the potential role of host macrophage Argonautes in Leishmania pathogenesis. Western blot analysis showed that protein abundance of infected macrophage Argonaute 1 (Ago1) was selectively and significantly higher than that of non-infected control at 24 h post-infection, suggesting that Ago1 plays a role in pathogenicity. In fact, siRNA-mediated downregulation of Ago1 enhanced Leishmania clearance from infected host cells, linking macrophage Ago1 to Leishmania virulence. To investigate the mechanisms of host Ago1 in Leishmania pathogenesis, a stable isotope labeling by amino acids in cell culture (SILAC)-based whole proteome approach was employed, which showed that expression of several previously reported Leishmania pathogenesis-related proteins were dependent on the level of macrophage Ago1. Moreover, the proteomic-based detailed biochemical analysis showed that Leishmania modulated host RNA-induced silencing complex (RISC) composition during infection, strongly suggesting macrophage RISC targeting. Strikingly, Leishmania proteins were detected as part of host RISC in infected cells. Together, our results demonstrate that Leishmania targets host RNA interference machinery to promote its survival inside the host macrophage.
Project description:The project aims at computing in vivo co-assembly kinetics from metabolomic-inspired approaches. In short, we performed reciprocal pull-down experiments from complex cellular components at different time points following pulsed-SILAC metabolic labeling. We applied the method to 320 pairs of yeast nucleoporin (NUP) proteins constituting the ~ 50 MDa Nuclear Pore Complex (NPC). Our analysis reveals a hierarchical principle of the NPC biogenesis where individual subcomplexes form on a minute time-scale, followed by their co-assembly from central to peripheral subunits in a ~ 1 hour long maturation process.
Project description:The current work identified the protein interactors of SARS-CoV-2 Nucleocapsid RNA binding protein (NCAP or N protein) in lung cancer A-549 cells, using a co-immunoprecipitation strategy, which is coupled with SILAC-based mass spec. A significant proportion of the identified NCAP interacting proteins included stress granule (SG) and immunoregulators. SG nucleator G3BP1 showed specific interaction wit NCAP in unstressed and oxidative- or heat-stressed cells. Following stress treatment, NCAP showed enhanced association with SGs. Recombinant NCAP exhibited in vitro liquid-liquid phase separation (LLPS)to form liquid droplets. RNA stimulated NCAP to develop droplets in vitro and SG assembly in cells, and RNase A treatment completely blocked both of these functions. An RNA intercalating mitoxantrone disrupted NCAP assembly in SGs invitro and in cells. This study provides insight into the biological processes and biophysical properties of the SARS-CoV-2 NCAP and identifies a candidate way to target this protein.
Project description:To understand the extent that Heat shock protein 90 (Hsp90) regulated its target proteins at the transcription level, transcriptomic change was profiled in yeast cells upon Hsp90 compromising. We genetically modified the R1158 strain (resulting genotype of mutant strain: TETp-HSC82 hsp82Δ arg4Δ lys5Δ car2Δ::URA3) and then reduced the Hsp90 amount with doxycycline treatment. Fold change of mRNA from untreated to treated cells indicated the transcriptomic change. Totally, we identified 1104 genes mis-regulated with a fold change of no less than 1.5 (P <0.05) upon Hsp90 compromising. Two-condition experiment, treated vs. untreated cells. Biological duplicates, independently grown and harvested. Technical triplicates for RNA isolation.