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Biomolecules, Volume 2, Issue 3 (September 2012), Pages 312-414

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Research

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Open AccessArticle SUMOylation in Giardia lamblia: A Conserved Post-Translational Modification in One of the Earliest Divergent Eukaryotes
Biomolecules 2012, 2(3), 312-330; doi:10.3390/biom2030312
Received: 16 June 2012 / Revised: 5 July 2012 / Accepted: 13 July 2012 / Published: 25 July 2012
Cited by 1 | PDF Full-text (1223 KB) | HTML Full-text | XML Full-text
Abstract
Post-translational modifications are able to regulate protein function and cellular processes in a rapid and reversible way. SUMOylation, the post-translational modification of proteins by the addition of SUMO, is a highly conserved process that seems to be present in modern cells. However, the
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Post-translational modifications are able to regulate protein function and cellular processes in a rapid and reversible way. SUMOylation, the post-translational modification of proteins by the addition of SUMO, is a highly conserved process that seems to be present in modern cells. However, the mechanism of protein SUMOylation in earlier divergent eukaryotes, such as Giardia lamblia, is only starting to become apparent. In this work, we report the presence of a single SUMO gene encoding to SUMO protein in Giardia. Monoclonal antibodies against recombinant Giardia SUMO protein revealed the cytoplasmic localization of native SUMO in wild-type trophozoites. Moreover, the over-expression of SUMO protein showed a mainly cytoplasmic localization, though also neighboring the plasma membrane, flagella, and around and even inside the nuclei. Western blot assays revealed a number of SUMOylated proteins in a range between 20 and 120 kDa. The genes corresponding to putative enzymes involved in the SUMOylation pathway were also explored. Our results as a whole suggest that SUMOylation is a process conserved in the eukaryotic lineage, and that its study is significant for understanding the biology of this interesting parasite and the role of post-translational modification in its evolution. Full article
(This article belongs to the Special Issue Protein SUMOylation)
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Review

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Open AccessReview SUMOylation in Drosophila Development
Biomolecules 2012, 2(3), 331-349; doi:10.3390/biom2030331
Received: 13 June 2012 / Revised: 23 June 2012 / Accepted: 25 June 2012 / Published: 25 July 2012
Cited by 3 | PDF Full-text (575 KB) | HTML Full-text | XML Full-text
Abstract
Small ubiquitin-related modifier (SUMO), an ~90 amino acid ubiquitin-like protein, is highly conserved throughout the eukaryotic domain. Like ubiquitin, SUMO is covalently attached to lysine side chains in a large number of target proteins. In contrast to ubiquitin, SUMO does not have a
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Small ubiquitin-related modifier (SUMO), an ~90 amino acid ubiquitin-like protein, is highly conserved throughout the eukaryotic domain. Like ubiquitin, SUMO is covalently attached to lysine side chains in a large number of target proteins. In contrast to ubiquitin, SUMO does not have a direct role in targeting proteins for proteasomal degradation. However, like ubiquitin, SUMO does modulate protein function in a variety of other ways. This includes effects on protein conformation, subcellular localization, and protein–protein interactions. Significant insight into the in vivo role of SUMOylation has been provided by studies in Drosophila that combine genetic manipulation, proteomic, and biochemical analysis. Such studies have revealed that the SUMO conjugation pathway regulates a wide variety of critical cellular and developmental processes, including chromatin/chromosome function, eggshell patterning, embryonic pattern formation, metamorphosis, larval and pupal development, neurogenesis, development of the innate immune system, and apoptosis. This review discusses our current understanding of the diverse roles for SUMO in Drosophila development. Full article
(This article belongs to the Special Issue Protein SUMOylation)
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Open AccessReview SUMO Wrestles with Recombination
Biomolecules 2012, 2(3), 350-375; doi:10.3390/biom2030350
Received: 10 June 2012 / Revised: 27 June 2012 / Accepted: 13 July 2012 / Published: 25 July 2012
Cited by 5 | PDF Full-text (1095 KB) | HTML Full-text | XML Full-text
Abstract
DNA double-strand breaks (DSBs) comprise one of the most toxic DNA lesions, as the failure to repair a single DSB has detrimental consequences on the cell. Homologous recombination (HR) constitutes an error-free repair pathway for the repair of DSBs. On the other hand,
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DNA double-strand breaks (DSBs) comprise one of the most toxic DNA lesions, as the failure to repair a single DSB has detrimental consequences on the cell. Homologous recombination (HR) constitutes an error-free repair pathway for the repair of DSBs. On the other hand, when uncontrolled, HR can lead to genome rearrangements and needs to be tightly regulated. In recent years, several proteins involved in different steps of HR have been shown to undergo modification by small ubiquitin-like modifier (SUMO) peptide and it has been suggested that deficient sumoylation impairs the progression of HR. This review addresses specific effects of sumoylation on the properties of various HR proteins and describes its importance for the homeostasis of DNA repetitive sequences. The article further illustrates the role of sumoylation in meiotic recombination and the interplay between SUMO and other post-translational modifications. Full article
(This article belongs to the Special Issue Protein SUMOylation)
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Open AccessReview Sumoylation and the DNA Damage Response
Biomolecules 2012, 2(3), 376-388; doi:10.3390/biom2030376
Received: 1 August 2012 / Revised: 23 August 2012 / Accepted: 24 August 2012 / Published: 4 September 2012
Cited by 7 | PDF Full-text (680 KB) | HTML Full-text | XML Full-text
Abstract
The cellular response to DNA damage involves multiple pathways that work together to promote survival in the face of increased genotoxic lesions. Proteins in these pathways are often posttranslationally modified, either by small groups such as phosphate, or by protein modifiers such as
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The cellular response to DNA damage involves multiple pathways that work together to promote survival in the face of increased genotoxic lesions. Proteins in these pathways are often posttranslationally modified, either by small groups such as phosphate, or by protein modifiers such as ubiquitin or SUMO. The recent discovery of many more SUMO substrates that are modified at higher levels in damage conditions adds weight to the accumulated evidence suggesting that sumoylation plays an important functional role in the DNA damage response. Here we discuss the significance of DNA damage-induced sumoylation, the effects of sumoylation on repair proteins, sumoylation dynamics, and crosstalk with other posttranslational modifications in the DNA damage response. Full article
(This article belongs to the Special Issue DNA Damage Response)
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Open AccessReview Comparative Studies of Vertebrate Platelet Glycoprotein 4 (CD36)
Biomolecules 2012, 2(3), 389-414; doi:10.3390/biom2030389
Received: 2 August 2012 / Revised: 6 September 2012 / Accepted: 18 September 2012 / Published: 24 September 2012
Cited by 2 | PDF Full-text (2103 KB) | HTML Full-text | XML Full-text
Abstract
Platelet glycoprotein 4 (CD36) (or fatty acyl translocase [FAT], or scavenger receptor class B, member 3 [SCARB3]) is an essential cell surface and skeletal muscle outer mitochondrial membrane glycoprotein involved in multiple functions in the body. CD36 serves as a ligand receptor of
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Platelet glycoprotein 4 (CD36) (or fatty acyl translocase [FAT], or scavenger receptor class B, member 3 [SCARB3]) is an essential cell surface and skeletal muscle outer mitochondrial membrane glycoprotein involved in multiple functions in the body. CD36 serves as a ligand receptor of thrombospondin, long chain fatty acids, oxidized low density lipoproteins (LDLs) and malaria-infected erythrocytes. CD36 also influences various diseases, including angiogenesis, thrombosis, atherosclerosis, malaria, diabetes, steatosis, dementia and obesity. Genetic deficiency of this protein results in significant changes in fatty acid and oxidized lipid uptake. Comparative CD36 amino acid sequences and structures and CD36 gene locations were examined using data from several vertebrate genome projects. Vertebrate CD36 sequences shared 53–100% identity as compared with 29–32% sequence identities with other CD36-like superfamily members, SCARB1 and SCARB2. At least eight vertebrate CD36 N-glycosylation sites were conserved which are required for membrane integration. Sequence alignments, key amino acid residues and predicted secondary structures were also studied. Three CD36 domains were identified including cytoplasmic, transmembrane and exoplasmic sequences. Conserved sequences included N- and C-terminal transmembrane glycines; and exoplasmic cysteine disulphide residues; TSP-1 and PE binding sites, Thr92 and His242, respectively; 17 conserved proline and 14 glycine residues, which may participate in forming CD36 ‘short loops’; and basic amino acid residues, and may contribute to fatty acid and thrombospondin binding. Vertebrate CD36 genes usually contained 12 coding exons. The human CD36 gene contained transcription factor binding sites (including PPARG and PPARA) contributing to a high gene expression level (6.6 times average). Phylogenetic analyses examined the relationships and potential evolutionary origins of the vertebrate CD36 gene with vertebrate SCARB1 and SCARB2 genes. These suggested that CD36 originated in an ancestral genome and was subsequently duplicated to form three vertebrate CD36 gene family members, SCARB1, SCARB2 and CD36. Full article
(This article belongs to the Special Issue Challenges in Glycan, Glycoprotein and Proteoglycan Research)
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