Urm1 couples sulfur transfer to ubiquitin-like protein function in oxidative stress.

Sanford-Burnham Medical Research Institute, La Jolla, CA 92037, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.81). 02/2011; 108(5):1749-50. DOI: 10.1073/pnas.1019043108
Source: PubMed
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    ABSTRACT: The post-translation addition of ubiquitin (Ub) and structurally related polypeptide modifiers to other intracellular constituents is now known to be an important intermediate driving a wide assortment of metabolic and regulatory processes in plants. Although the most common targets are other proteins, conjugation of specific modifiers to lipids and prenyl groups or participation in sulfur chemistry, tRNA modification, and RNA splicing also occur. The Ub system is clearly the most complex in terms of targets (~1000s) and underpinning enzymatic machinery (~6% of the Arabidopsis proteome), with its primary role to initiate the selective turnover of unwanted proteins by the 26S proteasome. However, recent studies revealed that several other modifiers also direct critical plant functions, especially with respect to autophagic recycling, the regulation of transcription and chromatin structure, and RNA metabolism. In fact, emerging studies have unearthed an intricate interplay between Ub and several of the Ub-like modifiers that sometimes works in synergy with or against ubiquitylation. While first thought to be restricted to eukaryotes, proteins related in structure and/or biochemistry to the Ub superfamily have been found in eubacteria and Archaea, indicating that this modification scheme evolved very early in cellular life, with prokaryotic sulfur transferase chemistry being the likely antecedent. Given their widespread distribution, diversity of targets, and multifaceted activities, Ub-type proteins are fast assuming their rightful places as fundamental regulators of plant biology.
    Plant physiology 06/2012; 160(1):2-14. · 7.39 Impact Factor
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    ABSTRACT: Ubiquitins are small peptides that allow for posttranslational modification of proteins. Ubiquitin-related modifier (URM) proteins belong to the class of ubiquitin-like proteins. A primary function of URM proteins has been shown to be the sulfur transfer reaction leading to thiolation of tRNAs, a process that is important for accurate and effective protein translation. Recent analyses revealed that the Arabidopsis genome codes for two URM proteins, URM11 and URM12, which both are active in the tRNA thiolation process. Here, we show that URM11 and URM12 have overlapping expression patterns and are required for tRNA thiolation. The characterization of urm11 and urm12 mutants reveals that the lack of tRNA thiolation induces changes in general root architecture by influencing the rate of lateral root formation. In addition, they synergistically influence root hair cell growth. During the sulfur transfer reaction, URM proteins of different organisms interact with a thiouridylase, a protein-protein interaction that also takes place in Arabidopsis, since URM11 and URM12 interact with the Arabidopsis thiouridylase ROL5. Hence, the sulfur transfer reaction is conserved between distantly related species such as yeast, humans, and plants, and in Arabidopsis has an impact on root development.
    PLoS ONE 01/2014; 9(1):e86862. · 3.53 Impact Factor
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    ABSTRACT: This review highlights the finding that ubiquitin-like (Ubl) proteins of archaea (termed SAMPs) function not only as sulfur carriers but also as protein modifiers. UbaA (an E1 ubiquitin-activating enzyme homolog of archaea) is required for the SAMPs to be covalently attached to proteins. The SAMPs and UbaA are also needed to form sulfur-containing biomolecules (e.g., thiolated tRNA and molybdenum cofactor). These findings provide a new perspective on how Ubl proteins can serve as both sulfur carriers and protein modifiers in the absence of canonical E2 ubiquitin conjugating or E3 ubiquitin ligase enzyme homologs.
    Trends in Microbiology 11/2012; · 9.81 Impact Factor

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