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Query: UMLS:C0009443 (cold)
 92,137 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The C-terminal domain (CTD) of the largest subunit of yeast RNA polymerase II contains 26-27 tandem copies of a conserved heptapeptide of unknown function. Yeast strains whose CTD contains ten heptamers are viable but defective for transcription of the INO1 gene and cold sensitive for growth. Deletion of the SIN1 gene, which codes for a DNA-binding protein that negatively regulates HO transcription, restores INO1 transcription and reduces the cold sensitivity of such strains. A SIN1 deletion suppresses the lethality of a CTD with nine heptamer repeats but not with seven repeats. These observations indicate a functional relationship between SIN1 and the CTD: the CTD might remove SIN1 from DNA, or removal of SIN1 may be a prerequisite for function of the CTD. The SWI1, SWI2, and SWI3 genes, whose products activate HO transcription by antagonizing SIN1, are also required for INO1 transcription and may assist the CTD. In addition, an intact CTD binds nonspecifically to DNA in vitro.
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PMID:A functional interaction between the C-terminal domain of RNA polymerase II and the negative regulator SIN1. 200 20

Differential screening of a cDNA library made from RNA extracted from avocado (Persea americana Mill cv. Hass) fruit stored at low temperature (7 degrees C) gave 23 cDNA clones grouped into 10 families, 6 of which showed increased expression during cold storage and normal ripening. Partial DNA sequencing was carried out for representative clones. Database searches found homologies with a polygalacturonase (PG), endochitinase, cysteine proteinase inhibitor and several stress-related proteins. No homologies were detected for clones from six families and their biological role remains to be elucidated. A full-length cDNA sequence for avocado PG was obtained and the predicted amino acid sequence compared with those from other PGs. mRNA encoding PG increased markedly during normal ripening, slightly later than mRNAs for cellulase and ethylene-forming enzyme (EFE). Low-temperature storage delayed ripening and retarded the appearance of mRNAs for enzymes known to be involved in cell wall metabolism and ethylene synthesis, such as cellulase, PG and EFE, and also other mRNAs of unknown function. The removal of ethylene from the atmosphere surrounding stored fruit delayed the appearance of the mRNAs encoding cellulase and PG more than the cold storage itself, although it hardly affected the expression of the EFE mRNA or the accumulation of mRNAs homologous to some other unidentified clones.
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PMID:Cloning and characterization of avocado fruit mRNAs and their expression during ripening and low-temperature storage. 809 63

Recent efforts have defined a cis-acting DNA regulatory element in plants, the C-repeat/dehydration responsive element (DRE), that stimulates transcription in response to low temperature and water deficit. Here we report the isolation of an Arabidopsis thaliana cDNA that encodes a C-repeat/DRE binding factor, CBF1 (C-repeat/DRE Binding Factor 1). Analysis of the deduced CBF1 amino acid sequence indicates that the protein has a molecular mass of 24 kDa, a potential nuclear localization sequence, and a possible acidic activation domain. CBF1 also has an AP2 domain, which is a DNA-binding motif of about 60 aa present in the Arabidopsis proteins APETALA2, AINTEGUMENTA, and TINY; the tobacco ethylene response element binding proteins; and numerous other plant proteins of unknown function. The transcript levels for CBF1, which appears to be a single or low copy number gene, did not change appreciably in plants exposed to low temperature or in detached leaves subjected to water deficit. Binding of CBF1 to the C-repeat/DRE was demonstrated in gel shift assays using recombinant CBF1 protein expressed in Escherichia coli. Moreover, expression of CBF1 in yeast was found to activate transcription of reporter genes containing the C-repeat/DRE as an upstream activator sequence but not mutant versions of the DNA element. We conclude that CBF1 can function as a transcriptional activator that binds to the C-repeat/DRE DNA regulatory element and, thus, is likely to have a role in cold- and dehydration-regulated gene expression in Arabidopsis.
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PMID:Arabidopsis thaliana CBF1 encodes an AP2 domain-containing transcriptional activator that binds to the C-repeat/DRE, a cis-acting DNA regulatory element that stimulates transcription in response to low temperature and water deficit. 902 78

The dnaG gene of Escherichia coli encodes the primase protein, which synthesizes a short pRNA that is essential for the initiation of both leading and lagging strand DNA synthesis. Two temperature-sensitive mutations in the 3' end of the dnaG gene, dnaG2903 and parB, cause a defect in chromosome partitioning at the nonpermissive temperature 42 degrees. We have characterized 24 cold-sensitive suppressor mutations of these two dnaG alleles. By genetic mapping and complementation, five different classes of suppressors have been assigned; sdgC, sdgD, sdgE, sdgG and sdgH. The genes responsible for suppression in four of the five classes have been determined. Four of the sdgC suppressor alleles are complemented by the dnaE gene, which encodes the enzymatic subunit of DNA polymerase III. The sdgE class are mutations in era, an essential GTPase of unknown function. The sdgG suppressor is likely a mutation in one of three genes: ubiC, ubiA or yjbI. The sdgH class affects rpsF, which encodes the ribosomal protein S6. Possible mechanisms of suppression by these different classes are discussed.
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PMID:Isolation and characterization of suppressors of two Escherichia coli dnaG mutations, dnaG2903 and parB. 909 42

The nucleotide and deduced amino acid sequence of a serine protease (AgSp24D) from the human malaria vector, Anopheles gambiae, is presented. The gene product is a 271 amino acid protein that contains the conserved serine, histidine and aspartic acid residues found in serine proteases, and has the highest identity to a serine protease of unknown function from Drosophila melanogaster. In situ hybridization to the polytene chromosomes detects a single band at 24D. Northern analysis reveals only low levels of transcripts in larvae and pupae, but more abundant transcription products occur in adults. Interestingly, this analysis also shows that adult males express much higher levels of AgSp24D mRNA than females. In addition, Plasmodium-refractory mosquitoes express higher levels of AgSp24D mRNA than susceptible mosquitoes although the biological significance of this remains to be examined. The thorax is the primary site for expression in the adults. The lack of a dramatic increase in AgSp24D mRNA levels following blood feeding suggests that this protease is not involved in digestive processes. Transcriptional induction does not follow cold shock, septic wounding, bacterial injection, laminarin injection or CM-Sephadex bead injection.
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PMID:Cloning and characterization of a serine protease from the human malaria vector, Anopheles gambiae. 935 80

The prnA gene codes for a transcriptional activator that mediates proline induction of four other genes involved in proline utilization as a nitrogen and/or carbon source in Aspergillus nidulans. In this paper, we present the genomic and cDNA sequence and the transcript map of prnA. The PrnA protein belongs to the Zn binuclear cluster family of transcriptional activators. The gene shows a striking intron-exon organization, with the putative nuclear localization sequence and the Zn cluster domain in discrete exons. Although the protein sequence presents some interesting similarities with the isofunctional protein of Saccharomyces cerevisiae Put3p, a higher degree of similarity is found with a functionally unrelated protein Thi1 of Schizosaccharomyces pombe. A number of mutations mapping in the prnA gene were sequenced. This comprises a deletion that results in an almost complete loss of the prnA-specific mRNA, a mutation in the putative nuclear localization signal, a proline to leucine mutation in the second loop of the zinc cluster and a cold-sensitive mutation in the so-called 'central region'. Other complete or partial loss of function mutations map in regions of unknown function. We establish that the transcription of the gene is neither self-regulated nor significantly affected by carbon and/or nitrogen metabolite repression.
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PMID:Sequence, exon-intron organization, transcription and mutational analysis of prnA, the gene encoding the transcriptional activator of the prn gene cluster in Aspergillus nidulans. 962 60

The signal recognition particle (SRP) is a ribonucleoprotein required for targeting a subset of nascent pre-secretory proteins to the endoplasmic reticulum membrane. Of the six SRP polypeptides, the most highly conserved is Srp54p, a modular protein consisting of an amino-terminal (N) domain of unknown function, a central GTPase (G) domain, and a carboxyl-terminal (M) domain implicated in the recognition of both signal sequences and SRP RNA. To identify regions of Srp54p that interact with other SRP subunits or regulatory proteins, we carried out systematic mutagenesis of the fission yeast homolog, principally using a "clustered charged-to-alanine" strategy. Of the 35 alleles examined, 13 are unable to support growth, two confer cold-sensitivity, five confer heat-sensitivity, and 15 produce no discernible phenotype. The lethal and conditional mutations map throughout the protein to several conserved regions, confirming that these motifs play critical roles in Srp54p function. The effects of the amino-acid substitutions are analyzed with reference to the recently determined tertiary structures of the N/G domain and the intact protein from a thermophilic bacterium.
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PMID:Systematic mutagenesis of the fission yeast Srp54 protein. 1007 27

To identify genes transcribed preferentially under salt stress, a subtractive RNA hybridization procedure was applied to the cyanobacterium Synechocystis sp. PCC 6803. The screening of a genomic library led to the identification of several RNA species that were more abundant in salt-stressed cells than in control cells. Salt-dependent transcription of the identified genes was verified in Northern blot experiments. In addition to the previously characterized genes cpn60 (encoding GroEL; a molecular chaperone) and isiA (encoding a chlorophyll-binding protein), genes encoding a protein of unknown function (slr0082) and a putative RNA helicase (slr0083) were identified as salt-regulated genes in Synechocystis. Genes slr0082 and slr0083, located at sites adjacent to each other on the Synechocystis chromosome, were transcribed from separate promoters and showed the most significant induction 1-3 h after salt shock. The salt-regulated promoters of these two genes were mapped. Genes cpn60, slr0082, and slr0083 were also found to be induced by a cold shock. The possible role of the identified gene products for salt adaptation of Synechocystis is discussed.
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PMID:Identification of salt-regulated genes in the genome of the cyanobacterium Synechocystis sp. strain PCC 6803 by subtractive RNA hybridization. 1059 47

Periplasmic proteins isolated by cold osmotic shock of Synechocystis sp. PCC 6803 cells were identified using 2D PAGE, MS and genome analysis. Most of the periplasmic proteins represent 'hypothetical proteins' with unknown function. A number of proteases of different specificity, and several enzymes involved in cell wall biosynthesis were also found. In salt-adapted cells, six proteins were greatly enhanced and three proteins were newly induced. Most of the salt-enhanced proteins are involved in the alteration of cell wall structure of salt-adapted cells. The precursors of all 57 periplasmic proteins identified have a signal peptide; 47 of them contain a typical Sec-dependent signal peptide, whereas 10 contain a putative twin-arginine signal peptide.
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PMID:Proteomics of Synechocystis sp. strain PCC 6803. Identification of periplasmic proteins in cells grown at low and high salt concentrations. 1099 49

Cold acclimation in plants is associated with the expression of COR (cold-regulated) genes that encode polypeptides of unknown function. It has been widely speculated that products of these genes might have roles in freezing tolerance. Here we provide direct evidence in support of this hypothesis. We show that constitutive expression of COR15a, a cold-regulated gene of Arabidopsis thaliana that encodes a chloroplast-targeted polypeptide, enhances the in vivo freezing tolerance of chloroplasts in nonacclimated plants by almost 2 degrees C, nearly one-third of the increase that occurs upon cold acclimation of wild-type plants. Significantly, constitutive expression of COR15a also affects the in vitro freezing tolerance of protoplasts. At temperatures between -5 and -8 degrees C, the survival of protoplasts isolated from leaves of nonacclimated transgenic plants expressing COR15a was greater than that of protoplasts isolated from leaves of nonacclimated wild-type plants. At temperatures between -2 and -4 degrees C, constitutive expression of COR15a had a slight negative effect on survival. The implications of these data regarding possible modes of COR15a action are discussed.
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PMID:Constitutive expression of the cold-regulated Arabidopsis thaliana COR15a gene affects both chloroplast and protoplast freezing tolerance. 1103 26


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