Project description:Histone-Lysine N-methyltransferase SETD2 is an evolutionarily conserved histone methyltransferase that associates with RNA Polymerase II (RNAPII) and catalyzes trimethylation of histone H3 lysine 36 (H3K36me3) in transcribed regions. Interestingly, SETD2 is frequently mutated in cancers. Clear cell renal cell carcinomas (ccRCCs) have extensive mutation of SETD2, implicating SETD2 as a tumor suppressor. ccRCCs are known for early driving events where the 3p chromosomal arm is lost, deleting one copy of SETD2, resulting in haploinsufficiency. While the role of SETD2 mediated H3K36me3 and interaction of RNAPII has been the focus of many studies, haploinsufficient SETD2 tumors retain H3K36me3, yet have drastic genome stability defects. The C-terminus of SETD2 is required for H3K36me3 while the N-terminus of SETD2 remains poorly characterized compared to the C-terminus. The N-terminus is highly disordered and has recently been shown to contribute to SETD2 stability, implicating regulatory functions. To better understand how SETD2 contributes to chromatin biology, we first sought to identify SETD2 protein interactors. A stable, immortalized normal human kidney epithelial cell (HKC) line with a dox inducible SETD2-APEX2 construct was used for a proximity-based biotinylation assay. Initial analysis yielded 2083 biotinylated proteins with significant enrichment (log2 fold change > 2 p-value < 0.05) in SETD2-APEX2 compared to control. Gene Ontology analysis of these interactors revealed enrichment of proteins involved in nuclear envelope functions, including lamin A/C, lamin B1, lamin B2 and emerin. These interactions were confirmed via western and reciprocal immunoprecipitation (IP). To determine effect of SETD2 depletion on lamin A/C and lamin B1 phosphorylation, we performed lamin A/C or lamin B1 IP from control or SETD2-knockdown (KD) cells and interrogated via LC-MS/MS. Mass spectrometry analysis revealed a significant decrease in lamin A/C S22 phosphorylation, and modest decrease in S390 phosphorylation, in SETD2 depleted cells compared to controls. While lamin B1 S23 phosphorylation was detected in control cells, we did not detect it in SETD2-KD cells, indicating a significant reduction in S23 phosphorylation upon SETD2 depletion. Next, we sought to identify the effect of SETD2 N-terminal deletion on the SETD2 protein interactome. We compared the protein interactors of dox inducible WT-SETD2 APEX2 fusion to an N-terminal deletion mutant of SETD2 (tSETD2-APEX2). Deletion of the N-terminus resulted in loss of lamin B1 and emerin interaction. Intriguingly, tSETD2 selectively associated with lamin C, whereas WT SETD2 interacted with both lamin A and C. These data together reveal an interaction with SETD2 and nuclear lamins. Further experiments revealed a role for the SETD2 N-terminus in facilitating the association of lamins with CDK1, thereby promoting lamin phosphorylation and depolymerization required for nuclear envelope disassembly during mitosis. Together, the data reveal a non-catalytic role of SETD2 during mitosis.
Project description:Comparison between WT Stm1, deltaN terminal and control AP-MS. The pulldown was performed with 3 biological indipendent replicates.
Project description:Pseudomonas aeruginosa is a difficult-to-treat Gram-negative bacterial pathogen causing life-threatening infections. Adaptive resistance (AR) to cationic peptide antibiotics such as polymyxin B impairs the therapeutic success. This self-protection is mediated by two component systems (TCS) consisting of a membrane-bound histidine kinase and an intracellular response regulator (RR). As phosphorylation of the key RR aspartate residue is transient during signaling and hydrolytically unstable, the study of these systems is challenging. Therefore, we applied a tailored reverse polarity chemical proteomic strategy to capture this transient modification and read-out RR phosphorylation in complex proteomes using a nucleophilic probe. An ideal trapping methodology was developed with a recombinant RR demonstrating the importance of fine-tuned acidic pH values to facilitate the attack on the aspartate carbonyl C-atom and prevent unproductive hydrolysis. Analysis of Bacillus subtilis and P. aeruginosa proteomes revealed the detection of multiple phosphoaspartate sites, which closely resembled the conserved RR sequence motif. With this validated strategy we dissected the signaling of dynorphin A, a human peptide stress hormone, which is sensed by P. aeruginosa to mediate AR. Intriguingly, our methodology identified CprR as an unprecedented RR in dynorphin A interkingdom signaling.
Project description:Type IVa pili (T4aP) are versatile bacterial cell surface structures that undergo extension/adhesion/retraction cycles powered by the cell envelope-spanning T4aP machine. In this machine, a complex composed of four minor pilins and PilY1 primes T4aP extension and is also present at the pilus tip mediating adhesion. Similar to many other bacteria, Myxococcus xanthus contains multiple minor pilins/PilY1 sets, the function of which remains unknown.Here, we report that minor pilins and PilY1 of cluster_1 (PilY1.1) form calcium-responsive priming and tip complexes contingent on a non-canonical cytochrome c (TfcP) with an unusual His/Cys heme ligation. We provide evidence that TfcP is unlikely to participate in electron transport and has been repurposed to promote calcium binding by PilY1.1 at low calcium concentrations, thereby stabilising PilY1.1 and enabling its function in a broader range of calcium concentrations. These results identify a novel function of cytochromes c and illustrate how incorporating an accessory factor expands the environmental range under which the T4aP system functions.
Project description:Using structural analysis together with affinity tagged purification mass spectrometry experiments, we identify Nsp2 mutants that are unable to interact with key host proteins and processes.