A Msp1-containing complex removes orphaned proteins in the mitochondrial outer membrane of <i>T. brucei</i>

The AAA-ATPase Msp1 extracts mislocalised outer membrane proteins and thus contributes to mitochondrial proteostasis. Using pulldown experiments, we show that trypanosomal Msp1 localises to both glycosomes and the mitochondrial outer membrane, where it forms a complex with four outer membrane proteins. The trypanosome-specific pATOM36 mediates complex assembly of α-helically anchored mitochondrial outer membrane proteins such as protein translocase subunits. Inhibition of their assembly triggers a pathway that results in the proteasomal digestion of unassembled substrates. Using inducible single, double, and triple RNAi cell lines combined with proteomic analyses, we demonstrate that not only Msp1 but also the trypanosomal homolog of the AAA-ATPase VCP are implicated in this quality control pathway. Moreover, in the absence of VCP three out of the four Msp1-interacting mitochondrial proteins are required for efficient proteasomal digestion of pATOM36 substrates, suggesting they act in concert with Msp1. pATOM36 is a functional analog of the yeast mitochondrial import complex complex and possibly of human mitochondrial animal-specific carrier homolog 2, suggesting that similar mitochondrial quality control pathways linked to Msp1 might also exist in yeast and humans

Ageing-dependent thiol oxidation reveals early oxidation of proteins with core proteostasis functions

Oxidative post-translational modifications of protein thiols are well recognized as a readily occurring alteration of proteins, which can modify their function and thus control cellular processes. The development of techniques enabling the site-specific assessment of protein thiol oxidation on a proteome-wide scale significantly expanded the number of known oxidation-sensitive protein thiols. However, lacking behind are large-scale data on the redox state of proteins during ageing, a physiological process accompanied by increased levels of endogenous oxidants. Here, we present the landscape of protein thiol oxidation in chronologically aged wild-type Saccharomyces cerevisiae in a time-dependent manner. Our data determine early-oxidation targets in key biological processes governing the de novo production of proteins, protein folding, and degradation, and indicate a hierarchy of cellular responses affected by a reversible redox modification. Comparison with existing datasets in yeast, nematode, fruit fly, and mouse reveals the evolutionary conservation of these oxidation targets. To facilitate accessibility, we integrated the cross-species comparison into the newly developed OxiAge Database

Comparative Analysis of <em>FLC</em> Homologues in Brassicaceae Provides Insight into Their Role in the Evolution of Oilseed Rape

<div><p>We identified nine <em>FLOWERING LOCUS C</em> homologues (<em>BnFLC</em>) in <em>Brassica napus</em> and found that the coding sequences of all <em>BnFLCs</em> were relatively conserved but the intronic and promoter regions were more divergent. The <em>BnFLC</em> homologues were mapped to six of 19 chromosomes. All of the <em>BnFLC</em> homologues were located in the collinear region of <em>FLC</em> in the <em>Arabidopsis</em> genome except <em>BnFLC.A3b</em> and <em>BnFLC.C3b,</em> which were mapped to noncollinear regions of chromosome A3 and C3, respectively. Four of the homologues were associated significantly with quantitative trait loci for flowering time in two mapping populations. The <em>BnFLC</em> homologues showed distinct expression patterns in vegetative and reproductive organs, and at different developmental stages. <em>BnFLC.A3b</em> was differentially expressed between the winter-type and semi-winter-type cultivars. Microsynteny analysis indicated that <em>BnFLC.A3b</em> might have been translocated to the present segment in a cluster with other flowering-time regulators, such as a homologue of <em>FRIGIDA</em> in <em>Arabidopsis.</em> This cluster of flowering-time genes might have conferred a selective advantage to <em>Brassica</em> species in terms of increased adaptability to diverse environments during their evolution and domestication process.</p> </div

Phylogenetic tree of <i>FLC</i> homologues from <i>Brassica</i>, <i>Arabidopsis</i>, <i>Raphanus</i>, and <i>Sinapis</i> species.

<p><i>BnFLC</i> homologues are highlighted in bold, and <i>AtMAF1</i> (<i>MADS AFFECTING FLOWERING 1</i> of <i>A. thaliana</i>, an <i>AtFLC</i>-like gene) was used as the outgroup. <i>Br</i>, <i>Brassica rapa</i>; <i>Bo</i>, <i>B. oleracea</i>; <i>Rs</i>, <i>Raphanus sativus</i> (radish); <i>Sa</i>, <i>Sinapis alba</i> (white mustard); <i>At</i>, <i>Arabidopsis thaliana</i>; <i>Al</i>, <i>A. lyrata</i>; <i>Ah</i>, <i>A. halleri</i>; <i>Aa</i>, <i>A. arenosa; As, A. suecica</i>. GenBank accession numbers are given in parentheses. Bootstrap support values are shown beside the branches.</p

<i>Brassica napus FLC</i> homologues, their map positions, and sequence identities compared with their orthologues in <i>B. rapa</i> or <i>B. oleracea.</i>

a<p>The sequences isolated from BACs are indicated by an asterisk, and those isolated from PCR-amplified genomic DNA are designated ‘gDNA’ with the parent indicated in parentheses (T, <i>B. napus</i> cv. Tapidor; N, <i>B. napus</i> cv. Ningyou7).</p>b<p>The obtained sequences were compared with that of <i>AtFLC</i> to define the regions of each <i>BnFLC</i> gene that were isolated.</p>c<p>To calculate sequence identities, indels (insertions or deletions) were excluded and for partial sequences of <i>BnFLC.C2</i> and <i>BnFLC.C3a,</i> the available region was used.</p>d<p>The letter and numeral in parentheses represent the linkage group followed by the ancestral block in which the <i>FLC</i> homologues are located.</p>e<p>The number of nonsynonymous nucleotide substitutions is shown in parentheses.</p>f<p>There was a fragment with higher-order structure in intron 1 of <i>BnFLC.A3a</i> for which we failed to obtain the sequence.</p

Quantitative real-time PCR analysis of expression patterns for four <i>BnFLC</i> homologues.

<p>Different letters above a bar indicate a significant difference (<i>P</i><0.05). Expression levels at the cotyledon stage were considered to be the control. Relative expression values of each <i>BnFLC</i> homologue were normalized with the reference gene <i>β-Actin.</i> (A) Comparison of the relative expression levels of <i>BnFLC</i> homologues in different tissues of the winter cultivar Tapidor. Samples underlined with a solid or dashed line were collected from nonvernalized and vernalized plants, respectively. (B) Relative expression levels of <i>BnFLCs</i> in leaves and cotyledons at different developmental stages in the semi-winter cultivar Ningyou7. No cold treatment was applied throughout all of the developmental stages. (C) Vernalization responsiveness of <i>BnFLC</i> homologues in Tapidor and Ningyou7. The relative fold change between four-week-old leaves (without vernalization) and seven-week-old leaves (four-week-old plants followed by three weeks of cold treatment) was measured.</p