Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P62988 (Ubiquitin)
 4,326 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have isolated a mutant, mts2, in the fission yeast Schizosaccharomyces pombe which is defective in chromosome segregation. The predicted amino-acid sequence of the cloned mts2+ gene product is 75% identical to the S4 subunit of the human 26S ATP/ubiquitin-dependent protease. The human S4 subunit complementary DNA expressed from an S. pombe expression plasmid can rescue an S. pombe mts2 gene disruption. Both observations demonstrate that the mts2+ gene is the S. pombe homologue of the human S4 subunit. In addition, we provide genetic evidence for a physical interaction between the S4 and the related S7 subunit in the 26S multiprotein protease. We show that polyubiquitin-conjugated proteins accumulate in the mts2 mutant at the restrictive temperature, demonstrating that the mutant has an in vivo defect in the ubiquitin-dependent proteolysis pathway. Finally, the phenotype for the mts2 mutant indicates that protein degradation by the 26S protease is essential not for entry into but for the completion of mitosis.
 ...
PMID:Defective mitosis due to a mutation in the gene for a fission yeast 26S protease subunit. 824 31

Ubiquitin modification of a variety of protein targets within the cell plays important roles in many cellular processes. Among these are regulation of gene expression, regulation of cell cycle and division, involvement in the cellular stress response, modification of cell surface receptors, DNA repair, and biogenesis of mitochondria and ribosomes. The best studied modification occurs in the ubiquitin-dependent proteolytic pathway. Degradation of a protein by the ubiquitin system involves two discrete steps. Initially, multiple ubiquitin molecules are covalently linked in an ATP-dependent mode to the protein substrate. The protein moiety of the conjugate is then degraded by a specific protease into free amino acids with the release of free and reutilizable ubiquitin. This process also requires energy. In addition, stable mono-ubiquitin adducts are also found intracellularly, for example, those involving nucleosomal histones. Despite the considerable progress that has been made in elucidating the mode of action and roles of the ubiquitin system, many problems remain unsolved. For example, very little is known about the cellular substrates of the system and the signals that target them for conjugation and degradation. The scope of this review is to summarize briefly what is currently known on the role of the ubiquitin system in protein turnover, and to discuss in detail the mechanisms involved in selection of substrates for conjugation and in degradation of ubiquitin-conjugated proteins.
 ...
PMID:The ubiquitin-mediated proteolytic pathway. 826 85

Analysis of gene expression in Trypanosoma cruzi has been impeded by the lack of efficient, stable, DNA-mediated transfection systems. We describe here the establishment of such a system for T. cruzi. Stable transformants were isolated following integration of the circular transforming plasmid into the chromosome by homologous recombination. Mutants with a disrupted PUB12.5 polyubiquitin gene, resulting from targeted integration of the plasmid vector, have been isolated. A mutant harboring the disrupted PUB12.5 gene lacks the intact PUB12.5 mRNA as well as transcripts corresponding to the truncated gene. Genomic Southern-blot analysis indicates that the inserted plasmid is tandemly repeated in each of the clones analyzed. A secondary recombination event in one clone resulted in a deletion within the 2.65 calmodulin-ubiquitin locus, encompassing the sequence from the CalA2 calmodulin gene to the PUB12.5 polyubiquitin gene.
 ...
PMID:Stable transformation of Trypanosoma cruzi: inactivation of the PUB12.5 polyubiquitin gene by targeted gene disruption. 838 Dec 5

Sequence analysis of a newly identified polyubiquitin gene (UBQ13) from the Columbia ecotype of Arabidopsis thaliana revealed that the gene contained a 3.9-kb insertion in the coding region. All subclones of the 3.9-kb insert hybridized to isolated mitochondrial DNA. The insert was found to consist of at least two, possibly three, distinct DNA segments from the mitochondrial genome. A 590-bp region of the insert is nearly identical to the Arabidopsis mitochondrial nad1 gene. UBQ13 restriction fragments in total cellular DNA from ecotypes Ler, No-0, Be-0, WS, and RLD were identified and, with the exception of Be-0, their sizes were equivalent to that predicted from the corresponding ecotype Columbia UBQ13 restriction fragment without the mitochondrial insert. Isolation by polymerase chain reaction and sequence determination of UBQ13 sequences from the other ecotypes showed that all lacked the mitochondrial insert. All ecotypes examined, except Columbia, contain intact open reading frames in the region of the insert, including four ubiquitin codons which Columbia lacks. This indicates that the mitochondrial DNA in UBQ13 in ecotype Columbia is the result of an integration event that occurred after speciation of Arabidopsis rather than a deletion event that occurred in all ecotypes except Columbia. This stable movement of mitochondrial DNA to the nucleus is so recent that there are few nucleotide changes subsequent to the transfer event. This allows for precise analysis of the sequences involved and elucidation of the possible mechanism. The presence of intron sequences in the transferred nucleic acid indicates that DNA was the transfer intermediate. The lack of sequence identity between the integrating sequence and the target site, represented by the other Arabidopsis ecotypes, suggests that integration occurred via nonhomologus recombination. This nuclear/organellar gene transfer event is strikingly similar to the experimentally accessible process of nuclear integration of introduced heterologous DNA.
 ...
PMID:Recent stable insertion of mitochondrial DNA into an Arabidopsis polyubiquitin gene by nonhomologous recombination. 838 44

We have isolated and determined DNA sequence for the 5'-flanking regions of three Arabidopsis thaliana polyubiquitin genes, UBQ3, UBQ10, and UBQ11. Comparison to cDNA sequences revealed the presence of an intron in the 5'-untranslated region at the same position immediately upstream of the initiator methionine codon in each of the three genes. An intron at this position is also present in two sunflower and two maize polyubiquitin genes. An intron is also found in the 5'-untranslated regions of several animal polyubiquitin genes, although the exact intron position is not conserved among them, and none are in the same position as those in the higher plant polyubiquitin genes. Chimeric genes containing the 5'-flanking regions of UBQ3, UBQ10, and UBQ11 in front of the coding regions for the reporter enzyme Escherichia coli beta-glucuronidase (GUS) were constructed. When introduced transiently into Arabidopsis leaves via microprojectile bombardment, all resulted in readily detectable levels of GUS activity that were quantitatively similar. The introns of UBQ3 and UBQ10 in the corresponding promoter fragments were removed by replacement with flanking cDNA sequences and chimeric genes constructed. These constructs resulted in 2.5- to 3-fold lower levels of marker enzyme activity after transient introduction into Arabidopsis leaves. The UBQ10 promoter without the 5' intron placed upstream of firefly luciferase (LUX) resulted in an average of 3-fold lower LUX activity than from an equivalent construct with the UBQ10 intron. A UBQ3 promoter cassette was constructed for the constitutive expression of open reading frames in dicot plants and it produced readily detectable levels of GUS activity in transient assays.
 ...
PMID:The intron of Arabidopsis thaliana polyubiquitin genes is conserved in location and is a quantitative determinant of chimeric gene expression. 838 9

Ubiquitin conjugating enzymes (E2s) are an integral part of a multienzyme pathway that ligates ubiquitin to intracellular target proteins. This ligation has been implicated in a number of fundamental processes including protein degradation, cell cycle progression, DNA repair, and organelle biogenesis. To function, E2s form a labile thiol-ester intermediate between a specific cysteine within the E2 and the carboxyl terminus of ubiquitin; this high energy intermediate then serves as the donor for ubiquitin ligation. To aid in the characterization of E2s, we have created a stable ubiquitin-E2 intermediate using a mutant form of the 16-kDa E2 encoded by the Arabidopsis thaliana AtUBC1 gene in which the active-site cysteine at residue 88 was replaced with serine. The mutant protein synthesized in Escherichia coli formed an adduct with ubiquitin in vitro, but in this case the E2 and ubiquitin were linked via a more stable ester bond. The ester-linked ubiquitin could not be transferred subsequently to substrate proteins in an E3 alpha-dependent conjugation reaction. The ester adduct was sufficiently stable to survive purification by anion exchange high performance liquid chromatography. As a result, this adduct may prove useful for the structural analysis of ubiquitin-E2 intermediates and in the study of E2s interacting with other ubiquitin pathway enzymes.
 ...
PMID:Formation of a stable adduct between ubiquitin and the Arabidopsis ubiquitin-conjugating enzyme, AtUBC1+. 838 69

During development, large numbers of cells die by a nonpathological process referred to as programmed cell death. In many tissues, dying cells display similar changes in morphology and chromosomal DNA organization, which has been termed apoptosis. Apoptosis is such a widely documented phenomenon that many authors have assumed all programmed cell deaths occur by this process. Two well-characterized model systems for programmed cell death are (i) the death of T cells during negative selection in the mouse thymus and (ii) the loss of intersegmental muscles of the moth Manduca sexta at the end of metamorphosis. In this report we compare the patterns of cell death displayed by T cells and the intersegmental muscles and find that they differ in terms of cell-surface morphology, nuclear ultrastructure, DNA fragmentation, and polyubiquitin gene expression. Unlike the T cells, which are known to die via apoptosis, we find that the intersegmental muscles display few of the features that characterize apoptosis. These data suggest that more than one cell death mechanism is used during development.
 ...
PMID:Do all programmed cell deaths occur via apoptosis? 843 Jan 12

We have developed a genetic screen of the yeast Saccharomyces cerevisiae to identify genes that act to coordinate DNA replication so that each part of the genome is copied exactly once per cell cycle. A mutant was recovered in this screen that accumulates aberrantly high DNA contents but does not complete a second round of synthesis. The mutation principally responsible for this phenotype is in the DOA4 gene, which encodes a ubiquitin hydrolase, one of several yeast genes that encode enzymes that can remove the signalling polypeptide ubiquitin hydrolase, one of several yeast genes that encode enzymes that can remove the signaling polypeptide ubiquitin from its covalently linked conjugated forms. DOA4 is nonessential, and deleting this gene causes uncoordinated replication. Overreplication does not occur in cells with limiting amounts of Cdc7 protein kinase, suggesting that entry into S phase is required for this phenotype. The DNA formed in doa4 mutants is not highly unusual in the sense that mitotic recombination rates are normal, implying that a high level of repair is not induced. The temperature sensitivity of doa4 mutations is partially suppressed by extra copies of the polyubiquitin gene UB14, but overreplication still occurs in the presence of this suppressor. Mutations in DOA4 cause loss of the free ubiquitin pool in cells under heat stress conditions, and extra copies of UB14 restore this pool without restoring coordination of replication. We conclude that a ubiquitin-mediated signaling event directly involving the ubiquitin hydrolase encoded by DOA4 is needed in S. cerevisiae to prevent uncoordinated DNA replication.
 ...
PMID:Coordinating DNA replication to produce one copy of the genome requires genes that act in ubiquitin metabolism. 865 9

The polyubiquitin gene from the mosquito Anopheles gambiae has been cloned and sequenced, and its structure is reported along with sequence analysis results. The gene consists of approximately seven tandem head-to-tail repeat units of the seventy-six amino acid-coding ubiquitin monomer. It is expressed constitutively in larvae, pupae and adults of An. gambiae, as well as in a cell line derived from this mosquito species. A probe made from a DNA fragment containing the coding region of the gene recognizes transcripts of approximately 3.6 kb and 4.4 kb in RNA isolated from all mosquito developmental stages and a unique transcript of approximately 3.0 kb in RNA from the cell line. Single monomeric units of the An. gambiae polyubiquitin gene shared from 75.9% to 85.5% identity at the DNA level with homologous sequences from other organisms ranging from yeast to man. A comparison of individual repeat units of the An. gambiae gene revealed that, in general, the 5' ends of the individual monomers are more highly conserved than the 3' ends. The gene mapped by in situ hybridization on ovarian nurse cell polytene chromosomes to a primary site at division 12C on chromosome 2R and to a secondary site at division 9C on the same chromosome.
 ...
PMID:The polyubiquitin gene of the mosquito Anopheles gambiae: structure and expression. 867 61

This report concerns retrospective immunohistochemical and immunoelectron microscopic studies on superoxide dismutase-1 (SOD1) in intracytoplasmic hyaline inclusions (IHIs) of the anterior horn cells of three patients with familial amyotrophic lateral sclerosis (ALS) with posterior column involvement. All of the patients were members of the American "C" family. Almost all of the IHIs, present in the soma and cordlike swollen neurites of some affected neurons of the three patients, were intensely stained by an antibody to human SOD1. By contrast, the cytoplasm of anterior horn cells of the ALS patients and of ten control individuals reacted only weakly with the antibody or not at all. Immunoelectron microscopy revealed that the granule-associated thick linear structures that composed the IHIs were intensely labeled by the antibody to SOD1. The IHIs were also positively stained by antibodies to ubiquitin and phosphorylated neurofilament protein, with the distribution of immunoreactivity resembling that seen with the anti-SOD1 antibody. The DNA analysis disclosed a single-site GCC to GTC substitution at codon 4 (Ala4 --> Val) in the SOD1 gene from the brain samples of the patients and from the peripheral blood of their family members. Our results suggest that SOD1 is a component of IHIs and may interact with Ubiquitin and neurofilament protein, and point to the possibility that the presence of intense SOD1 immunoreactivity in the IHIs may be of relevance in processes involving structurally altered SOD1 molecules encoded by the mutated gene.
 ...
PMID:Intense superoxide dismutase-1 immunoreactivity in intracytoplasmic hyaline inclusions of familial amyotrophic lateral sclerosis with posterior column involvement. 878 8


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>