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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Changes in gene expression induced by mechanical injury and heat shock were studied by comparing the expression of several stress-responsive gene families in potato tubers. The steady-state levels of mRNA-encoding ubiquitin, HSP70, and phenylalanine ammonia-lyase (PAL) increased and patatin transcript levels decreased within 45 minutes of impact injury. Nuclear runoff assays were used to demonstrate that the changes in steady-state transcript levels were due, at least in part, to changes in the rate of transcription for these genes. The observed changes in transcript levels were confined to the injured portion of the tuber. Treatment of tubers with exogenous ethylene elicited the same changes in the steady-state transcript levels as impact injury, indicating a potential role for this hormone in the injury-induced regulation of these genes. Two other forms of physical stress, heat shock and cutting injury, resulted in patterns of gene expression that are different from those induced by impact injury. The stress-induced regulation of these four gene families is complex, even though several characteristics of their expression are similar.
Plant Mol Biol 1991 Jun
PMID:Comparison of the expression of several stress-responsive genes in potato tubers. 165 Jun 14

Two ubiquitin genes, designated UbB1 and UbB2, were isolated from a sunflower genomic library. They encode polyubiquitin transcripts corresponding to six repeats of the monomer. Northern blot analysis identified several different transcript size classes: both UbB1 and UbB2 transcripts are found in the most abundant 1.6 kb class. In contrast to the previously isolated UbF transcript which is present at high levels in flowers, UbB1 and UbB2 are expressed constitutively at low levels in different tissues. The levels of the two transcripts increase after heat stress. The two genes exhibit strong homology suggesting that they may result from duplication and conversion. Surprisingly, UbB1 gene shows structural similarities with the chicken ubiquitin heat shock gene, in particular the presence of an intron located just in front of the first ATG.
Plant Mol Biol 1991 Sep
PMID:Structure and expression of sunflower ubiquitin genes. 165 59

The bacterial gene encoding beta-glucuronidase (GUS) was transiently expressed in cassava leaves following the introduction of the gene by microparticle bombardment. The DNA expression vector used to introduce the reporter gene is a pUC 19 derivative and consisted of a CaMV 35S promoter (P35S), the GUS coding region and 7S polyadenylation region. Several other promoters and regulating sequences were tested for efficiency in cassava leaves. Two derivatives of the P35S, one including a partial duplication of the upstream region of the P35S and the other containing a tetramer of the octopine synthase enhancer, were found to be expressed at three times the level of the P35S in cassava leaves. The ubiquitin 1 promoter from Arabidopsis thaliana was expressed at the same level as the P35S. No influence on the level of expression was observed when different 3' ends were used. The biolistic transient gene expression system in cassava leaves allows rapid analysis of gene constructs and can serve as a preliminary screen for chimeric gene function in the construction of transgenic cassava plants.
Plant Mol Biol 1991 Sep
PMID:Transient gene expression in cassava using high-velocity microprojectiles. 165 61

An in planta induced gene of Phytophthora infestans (the causal organism of potato late blight) was selected from a genomic library by differential hybridization using labelled cDNA derived from poly(A)+ RNA of P. infestans grown in vitro and labelled cDNA made from potato-P. infestans interaction poly(A)+ RNA as probes. Sequence analysis showed that the gene codes for ubiquitin, a highly conserved protein which plays an important role in several cellular processes. The structure of the polyubiquitin gene (designated ubi3R) is consistent with the structure of other known polyubiquitin genes. It consists of three repeats in a head-to-tail arrangement without intervening sequences, each encoding a ubiquitin unit of 76 amino acids. The last ubiquitin unit is followed by an extra asparagine residue at the carboxy-terminal end. Northern and Southern blot analyses revealed that the polyubiquitin gene is a member of a multigene family, all genes of which show induced expression in planta.
Plant Mol Biol 1991 Oct
PMID:An in planta induced gene of Phytophthora infestans codes for ubiquitin. 165 13

We report here the isolation and nucleotide sequence of tomato cDNA and genomic clones encoding a ubiquitin extension protein homologous to the yeast gene ubi3. Sites similar to upstream activating sites commonly found in the promoters of yeast ribosomal genes were observed in the tomato promoter. The tomato ubi3 promoter also contained elements found in the rbcS promoter from pea. The transcription initiation site was determined to occur 66 bp upstream of the initiating Met. RFLP mapping revealed that the gene was located on chromosome 1, 23 cM from marker TG301. A ubi3 gene-specific probe hybridized to a single 800 nt transcript. Expression was reduced in heat-shocked plants and plants kept in the dark. Expression was highest in young leaves and immature green fruit and lowest in mature leaves and petals. We isolated the original cDNA clone using an antibody prepared against chloroplast polypeptides. Immunological studies did not detect ubiquitin or ubiquitin extension proteins in the chloroplast. However, higher-molecular-weight chloroplast proteins were detected with ubiquitin antisera suggesting that ubiquitin conjugates are transported into the chloroplast.
Plant Mol Biol 1991 Dec
PMID:Isolation and characterization of tomato cDNA and genomic clones encoding the ubiquitin gene ubi3. 165 46

The RAD6 gene of Saccharomyces cerevisiae, which encodes a ubiquitin-conjugating enzyme, is required for DNA repair, DNA damage-induced mutagenesis and sporulation. To evaluate the biological relevance of the thioester adduct between RAD6 protein and ubiquitin, formed as an obligatory, transient intermediate during ubiquitin conjugation to substrates, we altered cysteine 88 in RAD6 to serine. Esterification with ubiquitin occurs at serine 88 in the mutant protein, but conjugation of ubiquitin to the test substrate histone H2A is inactivated. Phenotypically, strains harboring the rad6 Ser88 allele are indistinguishable from rad6 deletion (rad6 delta) mutant cells. These findings argue against ligation of ubiquitin at cysteine 88 acting as a functional switch of a cryptic biochemical activity in RAD6.
J Mol Biol 1991 Oct 05
PMID:Stable ester conjugate between the Saccharomyces cerevisiae RAD6 protein and ubiquitin has no biological activity. 165 33

The genome of Tetrahymena pyriformis has been shown to contain a ubiquitin multigene family consisting of several polyubiquitin genes and at least one ubiquitin fusion gene. We report here the isolation and characterization of one genomic clone (pTU11), that encodes a ubiquitin extension protein. A comparison of the predicted amino acid sequence of the ubiquitin extension protein gene of T. pyriformis with those from other organisms indicated a high degree of homology. However, the Tetrahymena ubiquitin extension protein contains 53 and not 52 amino acids. This feature is different from all ubiquitin 52-amino-acid extension protein genes thus far sequenced. Furthermore, we found an array of four cysteine residues similar to those found in nucleic acid binding proteins. Also, the C-terminal sequence possesses a conserved motif which may represent a nuclear translocation signal. The ubiquitin 53-amino-acid extension protein gene encodes the smallest class of ubiquitin mRNAs in T. pyriformis.
Mol Gen Genet 1991 Nov
PMID:Molecular cloning and expression of a Tetrahymena pyriformis ubiquitin fusion gene coding for a 53-amino-acid extension protein. 166 May 64

Ubiquitin is ubiquitous in all eukaryotes and its amino acid sequence shows extreme conservation. Ubiquitin genes comprise direct repeats of the ubiquitin coding unit with no spacers. The nucleotide sequences coding for 13 ubiquitin genes from 11 species reported so far have been compiled and analyzed. The G + C content of codon third base reveals a positive linear correlation with the genome G + C content of the corresponding species. The slope strongly suggests that the overall G + C content of codons of polyubiquitin genes clearly reflects the genome G + C content by AT/GC substitutions at the codon third position. The G + C content of ubiquitin codon third base also shows a positive linear correlation with the overall G + C content of coding regions of compiled genes, indicating the codon choices among synonymous codons reflect the average codon usage pattern of corresponding species. On the other hand, the monoubiquitin gene, which is different from the polyubiquitin gene in gene organization, gene expression, and function of the encoding protein, shows a different codon usage pattern compared with that of the polyubiquitin gene. From comparisons of the levels of synonymous substitutions among ubiquitin repeats and the homology of the amino acid sequence of the tail of monomeric ubiquitin genes, we propose that the molecular evolution of ubiquitin genes occurred as follows: Plural primitive ubiquitin sequences were dispersed on genome in ancestral eukaryotes. Some of them situated in a particular environment fused with the tail sequence to produce monomeric ubiquitin genes that were maintained across species. After divergence of species, polyubiquitin genes were formed by duplication of the other primitive ubiquitin sequences on different chromosomes. Differences in the environments in which ubiquitin genes are embedded reflect the differences in codon choice and in gene expression pattern between poly- and monomeric ubiquitin genes.
J Mol Evol 1991 Sep
PMID:Essential factors determining codon usage in ubiquitin genes. 166 81

Ubiquitin is involved in the degradation of denatured proteins in the recovery process after various stresses. To clarify the different responses of the ubiquitin system in the hippocampal neurons after ischemia, we chose 7.5 min of sublethal forebrain ischemia in the rat. After 7.5 min of ischemia, ubiquitin-like immunoreactivity (UIR) in most of the hippocampal pyramidal cells, except for the interneurons, diminished after 3 h of reperfusion, but enhanced UIR and subsequent recovery of UIR were observed in the different hippocampal regions after 24 h of reperfusion. The most prolonged recovery of UIR in the hippocampal cells was observed in the CA1 neurons after 72 h of reperfusion. Immunoblot analysis of the proteins extracted from CA1 region showed that high-mol-wt ubiquitin conjugates (HMWUC) above 40 kDa increased, whereas free ubiquitin and ubiquitinated histone 2A decreased slightly after 4 h and 24 h of reperfusion. At 72 h of reperfusion, HMWUC decreased to the original level and free ubiquitin slightly increased beyond the control level. These results suggested that (1) diminished UIR does not always mean depletion of entire ubiquitin-protein conjugates; (2) even after sublethal ischemia, damaged proteins in the CA1 neurons may increase, and it may take a long time for elimination of these proteins.
Mol Chem Neuropathol 1991 Aug
PMID:Changes in ubiquitin and ubiquitin-protein conjugates in the CA1 neurons after transient sublethal ischemia. 166 59

Considerable evidence suggests that altered neuronal calcium homeostasis plays a role in the neuronal degeneration that occurs in an array of neurological disorders. A reduction in microtubules, the accumulation of 8-15 nm straight filaments, and altered antigenicity toward antibodies to the microtubule-associated protein tau and ubiquitin, as well as granulovacuolar degeneration, are observed in many human neurodegenerative disorders. Progress toward understanding how and why human neurons degenerate has been hindered by the inability to examine living human neurons under controlled conditions. We used cultured human fetal cerebral cortical neurons to examine ultrastructural and antigenic changes resulting from elevations in intracellular calcium levels. Elevation of intracellular calcium by exposure to a calcium ionophore or a reduced level of extracellular Na+ for periods of hours to days caused a loss of microtubules, an increase in 8-15 nm straight filaments, and increased immunostaining with Alz-50 and 5E2 (tau antibodies) and ubiquitin antibodies. Granulovacuolar degeneration was also observed. Antigenic changes in tau were sensitive to phosphatases, and the electrophoretic mobility of tau was altered in cells exposed to calcium ionophore, indicating that tau was excessively phosphorylated as the result of elevated intracellular calcium levels. Colchicine also caused an accumulation of straight filaments and altered tau immunoreactivity, suggesting that a disruption of microtubules secondary to altered calcium homeostasis may be a key event leading to altered tau disposition and neuronal degeneration. These data demonstrate that aberrant rises in intraneuronal calcium levels can result in changes in the neuronal cytoskeleton similar to those seen in neurodegenerative disorders, and suggest that this experimental system will be useful in furthering our understanding of the cellular and molecular mechanisms of human neurological disorders.
Mol Chem Neuropathol 1991 Oct
PMID:Effects of elevated intracellular calcium levels on the cytoskeleton and tau in cultured human cortical neurons. 166 46


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