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.
Project description:Mitochondrial complex I is a redox-driven proton pump that generates most of the proton-motive force powering oxidative phosphorylation and ATP synthesis in eukaryotes. We report the structure of complex I from the thermophilic eukaryote Chaetomium thermophilum, determined by electron cryo-microscopy to 2.4 A resolution in the open and closed conformation. Complex I has two arms, the peripheral and membrane arm, forming an L-shape. The two conformations differ in the relative position of the two arms. The open-to-closed transition is accompanied by substantial conformational changes in the Q-binding cavity and the E-channel, and by the formation of an aqueous connection between the E-channel and an extensive aqueous passage inside the membrane arm. The observed similarities provide strong support for a conserved, common mechanism that applies across all species from fungi to mammals. Furthermore, the complex is inhibited by the detergent DDM, which binds reversibly to two sites in the Q-binding cavity.
Project description:A correct genome annotation is fundamental for research in the field of molecular and structural biology. The annotation of the reference genome of Chaetomium thermophilum has been reported previously, but it is limited to open reading frames (ORFs) of genes and contains only a few noncoding transcripts. In this study, we identified and annotated by deep RNA sequencing full-length transcripts of C.thermophilum. We identified 7044 coding genes and a large number of noncoding genes (n=4567). Astonishingly, 23% of the coding genes are alternatively spliced. We identified 679 novel coding genes and corrected the structural organization of more than 50% of the previously annotated genes. Furthermore, we substantially extended the Gene Ontology (GO) and Enzyme Commission (EC) lists, which provide comprehensive search tools for potential industrial applications and basic research. The identified novel transcripts and improved annotation will help understanding the gene regulatory landscape in C.thermophilum. The analysis pipeline developed here can be used to build transcriptome assemblies and identify coding and noncoding RNAs of other species. The new genome annotation of the GTF file can be found here.
