Project description:The experiment consists of M.hyp 232 cultures digests analyzed on two mass specs, LTQ Velos Pro and LTQ FT Ultra LTQ Velos Pro: Six cell culture replicates of M.hyo 232 were hydrophobically separated using tree detergents: Digitonin, Tween, and SDS. Each francion, including the insoluble pellet, was trypsin digested and then cleaned using an SCX trap follwed by a RP trap to remove detergents. Each fraction was sepated using a Dionex U3000 splitless nanoflow system operating at 333 nl per minute using a gradient of 2% ACN to 50% ACN in 4 hours. Eluate was analyzed using an LTQ Velos Pro mass spectrometer with 20 MS/MS scans of the 20 most intense peaks from each MS scan. Dynamic exclusion was enable for 3 minutes for each m/z with a repeat count of 1. LTQ FT Ultra: Two cell pellets for high resolution analysis were lysed and trypsin digested. Digested peptides were dried, resuspended in 20 mM KH2PO4, 20% ACN, pH 3 (Buffer A) in 2.5 µL and transferred to low retention vials in preparation for separation using an Ultimate 3000 configured for 2D-LC. Each sample was loaded at 15 µl/min onto an SCX microtrap for the first dimension of separation, involving SCX steps of Buffer A + 0, 5, 10, 15, 20, 25, 30, 40, 50, 100, 250, 500, and 1000 mM KCl. For the second dimension of separation, each eluted salt step was desalted with an inline peptide microtrap with 2% ACN, 0.1% FA at 5 µl/min. Once desalted, the microtrap was switched into line with a fritless nano column (75µm x ~10cm) containing C18 media (5µ, 200 Å Magic, Michrom). Peptides were eluted using a gradient of 2% to 36% ACN, 0.1% FA at 350 nl/min over 60 min and electrospray ionized for analysis using an LTQ FT Ultra mass spectrometer. A survey scan m/z 350-1750 was acquired in the FT ICR cell (Resolution = 100,000 at m/z 400, with an accumulation target value of 1,000,000 ions). Up to the 6 most abundant ions (>3,000 counts) with charge states > +2 were sequentially isolated and fragmented within the linear ion trap using collisionally induced dissociation with an activation q = 0.25 and activation time of 30 ms at a target value of 30,000 ions. M/z ratios selected for MS/ MS were dynamically excluded for 30 seconds. Analysis: X!tandem searches were performed using the Mycoplasma hyopneumoniae strain 232 reference protein set from NCBI. The only difference between the searches for the LTQ Velos and LTQ FT was the precursor mass tolenance being set to +-1500ppm and +-24ppm respectively. Decoy searches were performed and the data filtered at e-value <= 0.01 with single peptide proteins discarded. These results are included in the submission as two tab-delimited text files.
Project description:The thermophilic fungus Chaetomium thermophilum has been successfully used in the past for biochemical and high resolution structural studies of protein complexes, but subsequent functional analysis of these assemblies were hindered due to the lack of genetic tools in this thermophile, which are typically amenable in several other mesophilic eukaryotic model organisms, in particular the yeast Saccharomycers cerevisiae. Hence, we aimed to develop a regulatable gene-expression system in C. thermophilum, which might facilitate such in vivo studies, based on what we know about the galactose-inducible GAL promoter in yeast. To identify sugar-regulatable promoters in C. thermophilum, we performed comparative xylose- versus glucose-dependent gene expression studies, which uncovered a number of enzymes induced by xylose but repressed by glucose. Subsequently, we cloned the promoters of the two most stringently regulated genes, the xylosidase-like gene (XYL) and xylitol dehydrogenase (XDH), obtained from this genome-wide analysis in front of the thermostable YFP (yellow fluorescent protein) reporter. In this way, we could demonstrate xylose-dependent YFP expression by either western blotting or life cell imaging fluorescence microscopy. Prompted by these results, we finally expressed a well-characterized dominant-negative ribosome assembly factor mutant, rsa4 E117>D, under the control of the XDH promoter, which allowed us to induce a nuclear export defect of the pre-60S subunit when C. thermophilum cells were grown in xylose but not glucose containing medium. Altogether, our study recognized xylose-regulatable promoters in Chaetomium thermophilum, which may foster functional studies of genes of interest in this thermophilic eukaryotic model organism.