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Query: UNIPROT:P62988 (Ubiquitin)
 4,326 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Using a tobacco ubiquitin cDNA clone as a probe, a genomic clone in EMBL3 coding for a tobacco polyubiquitin protein was isolated. Southern blot hybridization of the genomic clone with the cDNA clone identified a BamHI/EcoRI fragment of 2.5 kb to contain the coding region of polyubiquitin, and thus the fragment was subcloned into a plasmid vector. Nucleotide sequence determination of the clone identified an open reading frame for the four head-to-tail repeats of ubiquitin monomer of 76 amino acids interrupted by an intron sequence of 55 nucleotides. The four ubiquitin units were completely conserved except for the extra glutamine at the carboxy terminus of the last ubiquitin monomer. At the 5'-region upstream of the open reading frame, a sequence of 630 nucleotides was determined. In this region, well-known regulatory sequences such as the CCAAT box, TATA box and heat-shock elements could not be located; instead, a region very rich in C and T and repeats of CA was noticed. In the 3'-downstream region of the open reading frame, a sequence of 474 nucleotides was determined which contained putative polyadenylation signals and a GU-rich region.
Mol Cells 1998 Feb 28
PMID:Structure of a polyubiquitin gene in Nicotiana tabacum. 957 40

Ubiquitin is highly conserved 76 amino acid protein involved, among other functions, in the selective degradation of proteins in the cell. From a tomato (Lycopersicon esculentum Mill. cv. Craigella) genomic library, we have isolated a clone encoding a polyubiquitin gene, designated ubq1-1 comprising seven repeats of ubiquitin and two C-terminal extension amino acids. The ubq1-1 gene contains an intron of 1128bp immediately upstream of the translation start codon. DNA sequence comparison revealed that the 5' and 3' non-coding regions of the tomato ubq1-1 gene are nearly identical to the sequence of a polyubiquitin cDNA clone isolated from potato (Garbarino et al., 1992; Plant Mol. Biol. 20, 235-244). The ubq1-1 gene is expressed in leaves to rather low levels in tomato, and the abundance of ubq1-1 transcripts is increased under heat shock conditions. For functional analyses, a chimeric gene construct containing the intron and 1.6kb of ubq1-1 sequence 5' to the intron fused to the gus reporter gene was introduced into the tobacco genome. In leaves of transgenic tobacco plants, reporter gene expression was generally lower from the ubq1-1 promoter than from the cauliflower mosaic virus 35S RNA promoter. In addition, the tomato ubq1-1 promoter was not found to respond to heat shock in transgenic tobacco plants. Histochemical analysis of the plants demonstrated localization of gus reporter gene activity in the vascular systems of the leaves and the roots. Deletion of the intron from the reporter gene construct markedly reduced reporter gene expression in transformed tobacco plants, thus suggesting that the intron may influence transcript levels deriving from the ubq1-1 promoter.
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PMID:Characterization and expression of a heptaubiquitin gene from tomato. 960 46

Four cDNA clones, named pSEN2, pSEN3, pSEN4, and pSEN5, for mRNAs induced during leaf senescence in Arabidopsis thaliana were characterized. The clones were isolated from a cDNA library of detached leaves incubated in darkness for 2 days to accelerate senescence, first by differential screening and then by examining expression of the primarily screened clones during age-dependent leaf senescence. Transcript levels detected by these cDNA clones, thus, were up-regulated in an age-dependent manner and during dark-induced leaf senescence. In contrast, when leaf senescence was induced by ethylene, ABA or methyljasmonate, the transcript level detected by the clones was differentially regulated depending on the senescence-inducing hormones. The transcript level for pSEN4 increased during senescence induced by all three hormones, while the transcript detected by the pSEN2 clone did not increase during senescence induced by ethylene. The transcript level for pSEN5 was increased upon ABA-induced senescence but decreased during ethylene-induced senescence. The pSEN3 clone detected multiple transcripts that are differentially regulated by these factors. The results show that, although the apparent senescence symptoms of Arabidopsis leaf appear similar regardless of the senescence-inducing factors, the detailed molecular state of leaf cells during senescence induced by different senescence-inducing factors is different. The pSEN3 clone encodes a polyubiquitin and the pSEN4 clone encodes a peptide related to endoxyloglucan transferase. This result is consistent with the expected roles of senescence-induced genes during leaf senescence.
Plant Mol Biol 1998 Jun
PMID:Differential expression of senescence-associated mRNAs during leaf senescence induced by different senescence-inducing factors in Arabidopsis. 961 12

Modification of an S. cerevisiae G protein-coupled receptor with ubiquitin is required for its ligand-stimulated internalization. We now demonstrate that monoubiquitination on a single lysine residue is sufficient to signal receptor internalization, a modification distinct from that required for proteasome recognition. Formation of a polyubiquitin chain is not necessary, as demonstrated by the ability of mutant ubiquitins that lack lysine residues to serve as efficient internalization signals. Fusion of ubiquitin in-frame to a receptor that lacks cytoplasmic tail lysines also promotes rapid receptor internalization, indicating that ubiquitin itself and not a specific type of linkage to the receptor acts as an internalization signal. Thus, we have defined a cellular function for monoubiquitination in alpha-factor receptor endocytosis.
Mol Cell 1998 Jan
PMID:A function for monoubiquitination in the internalization of a G protein-coupled receptor. 965 16

Ubiquitin-mediated proteolysis is the key to cell cycle control. Anaphase-promoting complex/cyclosome (APC) is a ubiquitin ligase that targets cyclin B and factors regulating sister chromatid separation for proteolysis by the proteasome and, consequently, regulates metaphase-anaphase transition and exit from mitosis. Here we report that Cdc2-cyclin B-activated Polo-like kinase (Plk) specifically phosphorylates at least three components of APC and activates APC to ubiquitinate cyclin B in the in vitro-reconstituted system. Conversely, protein kinase A (PKA) phosphorylates two subunits of APC but suppresses APC activity. PKA is superior to Plk in its regulation of APC, and Plk activity peaks whereas PKA activity is falling at metaphase. These results indicate that Plk and PKA regulate mitosis progression by controlling APC activity.
Mol Cell 1998 Feb
PMID:PKA and MPF-activated polo-like kinase regulate anaphase-promoting complex activity and mitosis progression. 966 Sep 21

We compared the effect of burn injury on the energy-ubiquitin-dependent proteolytic pathway in the fast-twitch extensor digitorum longus (EDL) and the slow-twitch soleus muscle in rats. Rats were subjected to a 30% total body surface area full-thickness burn or sham procedure. At various time points after injury, total and myofibrillar protein breakdown rates were determined in incubated EDL and soleus muscles. The energy-dependent component of protein break-down was determined by incubating muscles in energy-depleting medium. Messenger RNA levels for ubiquitin and RC3, a 20S proteasome subunit, were measured by Northern blot analysis. Burn injury resulted in an approximately 50% increase in total protein breakdown and a 3-4 fold increase in myofibrillar protein breakdown in EDL muscles, and this response reflected increased energy-dependent protein breakdown. In contrast, protein breakdown rates were not significantly influenced by the burn injury in soleus muscles. Ubiquitin mRNA levels were increased almost 10-fold in EDL and approximately 4.5-fold in soleus muscles following burn injury. Burn injury resulted in a 2-fold increase in RC3 mRNA in EDL with no significant changes noted in soleus muscles. The results suggest that the more pronounced effect of burn injury on protein breakdown in fast-twitch than in slow-twitch muscle may reflect different regulation of proteolysis at the molecular level.
Int J Mol Med 1998 Jan
PMID:The molecular regulation of protein breakdown following burn injury is different in fast- and slow-twitch skeletal muscle. 985 15

Ubiquitin (Ub) is a highly conserved small protein present universally in eukaryotic cells, which is covalently attached to substrate proteins by a cascade system, consisting of activating (E1), conjugating (E2), and/or ligating (E3) enzymes. The modification of cellular proteins with Ub targets them for degradation by a large multisubunit protease, called the 26S proteasome. The unexpected existence of many genes encoding E2 and E3 reveals that a number of distinct Ub-ligating pathways operate for selective proteolysis in cells, implying its involvement in divergent biologically important processes. Currently, it becomes clear that a set of novel molecules with a structural similarity to Ub, called Ub-like proteins (Ubls), is present in various eukaryotic cells. They are divided into two subclasses: type-1 Ubls with small sizes, such as SUMO1 and NEDD8, that are ligated to target proteins in a fashion similar, but not identical, to the ubiquitination pathway, and another type-2 Ubls that contain Ub-like structure in a variety of different classes of large proteins having apparently distinct functions, such as Rad23, Elongin B, and Parkin. Ub and type-1 Ubls are central players consisting of a new type of post-translational protein-modifying system, although the significance of type-2 Ubl remains obscure.
Mol Cells 1998 Oct 31
PMID:The ligation systems for ubiquitin and ubiquitin-like proteins. 985 35

We have identified 39 Arabidopsis thaliana ESTs encoding germin-like proteins (GLPs) and have completely sequenced 25 of these cDNAs. Our analysis demonstrates that the Arabidopsis genome contains a gene family with at least 12 GLP genes. Comparisons with other known germins and germin-like proteins indicate that these Arabidopsis GLP subfamilies are unique from wheat germin. All other known GLPs fall into one of these subfamilies. The translated GLPs show approximately 35% amino acid identity with other GLPs outside of their subfamily and significantly higher levels of identity within their respective subfamily. The 3' ends of many of the GLP cDNAs are heterogeneous and several sites of polyadenylation are used. Ten of the GLPs have N-terminal signal sequences and most appear to be exported from the cell. Structurally, the GLPs are predicted to have a high content of beta-pleated sheet. Seven conserved regions of beta-sheet were found in each of the GLP proteins along with alpha-helices located at both N- and C-termini. These same structural elements are also conserved in wheat germin. With one exception, all GLP family members contain at least one N-glycosylation site. All of these sites are conserved in an unstructured loop between beta-1 and beta-2. Genes for two of these GLPs were identified in genomic sequences previously deposited in the GenBank. The GLP3b gene is physically linked to the polyubiquitin 4 gene. The 3' end of the GLP3b mRNA is only 0.5 kb from the ubq4 start of transcription. Analysis of the GLP3b promoter shows the presence of a single putative auxin-response sequence located at -124 to -111 upstream from the 5' end of the GLP3b mRNA. The GLP9 gene was identified in an Arabidopsis contig from Chromosome 4.
Plant Mol Biol 1998 Dec
PMID:Arabidopsis thaliana contains a large family of germin-like proteins: characterization of cDNA and genomic sequences encoding 12 unique family members. 986

Transcription of the polyubiquitin gene UBI4 of Saccharomyces cerevisiae is strongly induced by a variety of environmental stresses, such as heat shock, nutrient depletion and exposure to DNA-damaging agents. This transcriptional response of UBI4 is likely to be the primary mechanism for increasing the pool of ubiquitin for degradation of stress-damaged proteins. Deletion and promoter fusion studies of the 5' regulatory sequences indicated that two different elements, heat shock elements (HSEs) and stress response element (STREs), contributed independently to heat shock regulation of the UBI4 gene. In the absence of HSEs, STRE sequences localized to the intervals -264 to -238 and -215 to -183 were needed for stress control of transcription after heat shock. Site-directed mutagenesis of the STRE (AG4) at -252 to -248 abolished heat shock induction of UBI4 transcription. Northern analysis demonstrated that cells containing either a temperature-sensitive HSF or non-functional Msn2p/Msn4p transcription factors induced high levels of UBI4 transcripts after heat shock. In cells deficient in both heat stress pathways, heat-induced UBI4 transcript levels were considerably lower but not abolished, suggesting a role for another factor(s) in stress control of its expression.
Mol Microbiol 1999 Feb
PMID:Multiple independent regulatory pathways control UBI4 expression after heat shock in Saccharomyces cerevisiae. 1004 26

We have identified two highly conserved RING finger proteins, ROC1 and ROC2, that are homologous to APC11, a subunit of the anaphase-promoting complex. ROC1 and ROC2 commonly interact with all cullins while APC11 specifically interacts with APC2, a cullin-related APC subunit. YeastROC1 encodes an essential gene whose reduced expression resulted in multiple, elongated buds and accumulation of Sic1p and Cln2p. ROC1 and APC11 immunocomplexes can catalyze isopeptide ligations to form polyubiquitin chains in an E1- and E2-dependent manner. ROC1 mutations completely abolished their ligase activity without noticeable changes in associated proteins. Ubiquitination of phosphorylated I kappa B alpha can be catalyzed by the ROC1 immunocomplex in vitro. Hence, combinations of ROC/APC11 and cullin proteins proteins potentially constitute a wide variety of ubiquitin ligases.
Mol Cell 1999 Apr
PMID:ROC1, a homolog of APC11, represents a family of cullin partners with an associated ubiquitin ligase activity. 1023 Apr 7


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