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

Helicases are ubiquitous molecular motor proteins that play important role in maintaining the genome integrity and thus involved in plant growth and development. Here, we report the cloning of cDNA (1.64 kb) and genomic DNA (2.2 kb) of cold stress-induced pea DNA helicase 47 (PDH47) and characterization of its encoded protein. It belongs to DEAD-box protein family and shows striking identity (93%) with tobacco eIF4A. The transcript was induced under cold (4 degrees C) stress. The purified PDH47 protein (47 kDa) contains ATP-/Mg2+-dependent DNA unwinding as well as DNA-/Mg2+-dependent ATPase activities. The ATPase activity of PDH47 is stimulated more by ssDNA as compared to dsDNA and RNA. The activities of PDH47 are inhibited by various DNA-interacting ligands such as nogalamycin, daunorubicin, ethidium bromide, mitoxantrone, actinomycin, and cisplatin with apparent Ki values ranging from 0.5 to 8.0 microM. Interestingly, netropsin and distamycin inhibited the helicase but not the ATPase activity. The inhibition might be due to the intercalation of inhibitors into duplex DNA, which can impede the translocation of the PDH47. This study should help in our better understanding of cold stress signaling and mechanism of DNA unwinding in plants.
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PMID:Cold stress-induced pea DNA helicase 47 is homologous to eIF4A and inhibited by DNA-interacting ligands. 1600 26

Helicases are involved in the metabolism of nucleic acid; this is very sensitive to the abiotic stresses that reduce plant growth and productivity. However, the molecular targets responsible for this sensitivity have not been well studied. Here we report on the isolation and characterization of cold- and salinity stress-induced pea DNA helicase 47 (PDH47). The transcript of PDH47 was induced in both shoots and roots under cold (4 degrees C) and salinity (300 mm NaCl) stress, but there was no change in response to drought stress. Tissue-specific differential regulation was observed under heat (37 degrees C) stress. ABA treatment did not alter expression of PDH47 in shoots but induced its mRNA in roots, indicating a role for PDH47 in both the ABA-independent and ABA-dependent pathways in abiotic stress. The purified recombinant protein (47 kDa) contains ATP-dependent DNA and RNA helicase and DNA-dependent ATPase activities. With the help of photoaffinity labeling, PDH47 was labeled by [alpha-32P]-ATP. PDH47 is a unique bipolar helicase that contains both 3' to 5' and 5' to 3' directional helicase activities. Anti-PDH47 antibodies immunodeplete the activities of PDH47 and inhibit in vitro translation of protein. Furthermore, the PDH47 protein showed upregulation of protein synthesis. The activities of PDH47 are stimulated after phosphorylation by protein kinase C at Ser and Thr residues. Western blot analysis and in vivo immunostaining, followed by confocal microscopy, showed PDH47 to be localized in both the nucleus and cytosol. The discovery of cold- and salinity stress-induced DNA helicase should make an important contribution to a better understanding of DNA metabolism and stress signaling in plants. Its bipolar helicase activities may also be involved in distinct cellular processes in stressed conditions.
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PMID:Cold- and salinity stress-induced bipolar pea DNA helicase 47 is involved in protein synthesis and stimulated by phosphorylation with protein kinase C. 1616 97

The nucleic acid binding cold shock proteins (CSPs) and the cold-induced DEAD box RNA helicases have been proposed separately to act as RNA chaperones, but no experimental evidence has been reported on a direct cooperation. To investigate the possible interaction of the putative RNA helicases CshA and CshB and the CSPs from Bacillus subtilis during cold shock, we performed genetic as well as fluorescence resonance energy transfer (FRET) experiments. Both cshA and cshB genes could be deleted only in the presence of a cshB copy in trans, showing that the presence of one csh gene is essential for viability. The combined gene deletion of cshB and cspD resulted in a cold-sensitive phenotype that was not observed for either helicase or csp single mutants. In addition to the colocalization of the putative helicases CshA and CshB with CspB and the ribosomes in areas surrounding the nucleoid, we detected a strong FRET interaction in vivo between CshB and CspB that depended on active transcription. In contrast, a FRET interaction was not observed for CshB and the ribosomal protein L1. Therefore, we propose a model in which the putative cold-induced helicases and the CSPs work in conjunction to rescue misfolded mRNA molecules and maintain proper initiation of translation at low temperatures in B. subtilis.
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PMID:Cold-induced putative DEAD box RNA helicases CshA and CshB are essential for cold adaptation and interact with cold shock protein B in Bacillus subtilis. 1635 40

The precise machineries required for two aspects of eukaryotic DNA replication, Okazaki fragment processing (OFP) and telomere maintenance, are poorly understood. In this work, we present evidence that Saccharomyces cerevisiae Pif1 helicase plays a wider role in DNA replication than previously appreciated and that it likely functions in conjunction with Dna2 helicase/nuclease as a component of the OFP machinery. In addition, we show that Dna2, which is known to associate with telomeres in a cell-cycle-specific manner, may be a new component of the telomere replication apparatus. Specifically, we show that deletion of PIF1 suppresses the lethality of a DNA2-null mutant. The pif1delta dna2delta strain remains methylmethane sulfonate sensitive and temperature sensitive; however, these phenotypes can be suppressed by further deletion of a subunit of pol delta, POL32. Deletion of PIF1 also suppresses the cold-sensitive lethality and hydroxyurea sensitivity of the pol32delta strain. Dna2 is thought to function by cleaving long flaps that arise during OFP due to excessive strand displacement by pol delta and/or by an as yet unidentified helicase. Thus, suppression of dna2delta can be rationalized if deletion of POL32 and/or PIF1 results in a reduction in long flaps that require Dna2 for processing. We further show that deletion of DNA2 suppresses the long-telomere phenotype and the high rate of formation of gross chromosomal rearrangements in pif1Delta mutants, suggesting a role for Dna2 in telomere elongation in the absence of Pif1.
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PMID:Evidence suggesting that Pif1 helicase functions in DNA replication with the Dna2 helicase/nuclease and DNA polymerase delta. 1653 95

Abiotic stresses including various environmental factors adversely affect plant growth and limit agricultural production worldwide. Minimizing these losses is a major area of concern for all countries. Therefore, it is desirable to develop multi-stress tolerant varieties. Salinity, drought, and cold are among the major environmental stresses that greatly influence the growth, development, survival, and yield of plants. UV-B radiation of sunlight, which damages the cellular genomes, is another growth-retarding factor. Several genes are induced under the influence of various abiotic stresses. Among these are DNA repair genes, which are induced in response to the DNA damage. Since the stresses affect the cellular gene expression machinery, it is possible that molecules involved in nucleic acid metabolism including helicases are likely to be affected. The light-driven shifts in redox-potential can also initiate the helicase gene expression. Helicases are ubiquitous enzymes that catalyse the unwinding of energetically stable duplex DNA (DNA helicases) or duplex RNA secondary structures (RNA helicases). Most helicases are members of DEAD-box protein superfamily and play essential roles in basic cellular processes such as DNA replication, repair, recombination, transcription, ribosome biogenesis and translation initiation. Therefore, helicases might be playing an important role in regulating plant growth and development under stress conditions by regulating some stress-induced pathways. There are now few reports on the up-regulation of DEAD-box helicases in response to abiotic stresses. Recently, salinity-stress tolerant tobacco plants have already been raised by overexpressing a helicase gene, which suggests a new pathway to engineer plant stress tolerance [N. Sanan-Mishra, X.H. Pham, S.K. Sopory, N. Tuteja, Pea DNA helicase 45 overexpression in tobacco confers high salinity tolerance without affecting yield. Proc. Natl. Acad. Sci. USA 102 (2005) 509-514]. Presently the exact mechanism of helicase-mediated stress tolerance is not understood. In this review we have described all the reported stress-induced helicases and also discussed the possible mechanisms by which they can provide stress tolerance.
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PMID:Stress responsive DEAD-box helicases: a new pathway to engineer plant stress tolerance. 1662 68

RNA helicases function as molecular motors that rearrange RNA secondary structure, potentially performing roles in any cellular process involving RNA metabolism. Although RNA helicase association with a range of cellular functions is well documented, their importance in response to abiotic stress is only beginning to emerge. This review summarizes the available data on the expression, biochemistry and physiological function(s) of RNA helicases regulated by abiotic stress. Examples originate primarily from non-mammalian organisms while instances from mammalian sources are restricted to post-translational regulation of helicase biochemical activity. Common emerging themes include the requirement of a cold-induced helicase in non-homeothermic organisms, association and regulation of helicase activity by stress-induced phosphorylation cascades, altered nuclear-cytoplasmic shuttling in eukaryotes, association with the transcriptional apparatus and the diversity of biochemical activities catalyzed by a subgroup of stress-induced helicases. The data are placed in the context of a mechanism for RNA helicase involvement in cellular response to abiotic stress. It is proposed that stress-regulated helicases can catalyze a nonlinear, reversible sequence of RNA secondary structure rearrangements which function in RNA maturation or RNA proofreading, providing a mechanism by which helicase activity alters the activation state of target RNAs through regulation of the reaction equilibrium.
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PMID:RNA helicases and abiotic stress. 1679 May 67

The Escherichia coli cold shock protein CsdA is a member of the DEAD box family of ATP-dependent RNA helicases, which share a core of nine conserved motifs. The DEAD (Asp-Glu-Ala-Asp) motif for which this family is named has been demonstrated to be essential for ATP hydrolysis. We show here that CsdA exhibits in vitro ATPase and helicase activities in the presence of short RNA duplexes with either 3' or 5' extensions at 15 degrees C. In contrast to wild-type CsdA, a DQAD variant of CsdA (Glu-157-->Gln) had no detectible helicase or ATPase activity at 15 degrees C in vitro. A plasmid encoding the DQAD variant was also unable to suppress the impaired growth of the csdA null mutant at 15 degrees C. Plasmid-encoded CsdADelta444, which lacks most of the carboxy-terminal extension, enhanced the growth of a csdA null mutant at 25 degrees C but not at 15 degrees C; this truncated protein also has limited in vitro activity at 15 degrees C. These results support the physiological function of CsdA as a DEAD box ATP-dependent RNA helicase at low temperature.
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PMID:Mutational analysis of the Escherichia coli DEAD box protein CsdA. 1725 9

Assembly of heterochromatin at centromeric DNA regions in the fission yeast Schizosaccharomyces pombe involves an intimate interplay between chromatin modifying complexes and components of the RNAi pathway. The RNA-induced transcriptional silencing (RITS) complex, containing Chp1, Ago1, Tas3, and centromeric siRNAs, localizes to centromeric DNA repeats and is required for the assembly and maintenance of heterochromatin. RITS brings together two types of molecular recognition modules: a chromodomain protein, which binds to lysine 9 methylated histone H3 (H3K9), and Argonaute, which binds to specific sequences by siRNA-directed base-pairing interactions. The RNA-directed RNA polymerase complex (RDRC), composed of Rdp1, the Hrr1 helicase, and the Cid12 Poly(A) polymerase family member, synthesizes double-stranded RNA and creates the substrate for Dicer to generate siRNAs. RDRC physically associates with RITS, and both complexes localize to noncoding centromeric RNAs and centromeric DNA repeats, suggesting that recognition of nascent RNA transcripts may be involved in localization of these complexes to specific chromosome regions. In support of this possibility, tethering of the RITS complex to the transcript of the normally euchromatic ura4 (+) gene results in siRNA generation and RNAi- and heterochromatin-dependent silencing of the ura4 (+) gene. Finally, silencing of a subset of endogenous and transgene promoters within heterochromatic DNA domains occurs by RNAi-dependent degradation of nascent transcripts by a mechanism that we have termed co-transcriptional gene silencing (CTGS).
Cold Spring Harb Symp Quant Biol 2006
PMID:Studies on the mechanism of RNAi-dependent heterochromatin assembly. 1738 28

An automated multidimensional protein identification technology, which combines biphasic liquid chromatography with electrospray ionisation tandem mass spectrometry (MS/MS), was employed to analyse tryptic peptides from Escherichia coli cells treated with the antiproliferation agent [(eta(6)-p-cymene)RuCl(2)(DMSO)], where DMSO is dimethyl sulfoxide. MS/MS spectra were recorded for molecular ions generated by neutral loss of p-cymene from intensive peptide ions coordinated by the (eta(6)-p-cymene)Ru(II) fragment. Matching of the MS/MS spectra of the ruthenated peptides to spectra of proteins in the E. coli database enabled the identification of five protein targets for [(eta(6)-p-cymene)RuCl(2)(DMSO)]. One of these is the constitutive cold-shock protein cspC, which regulates the expression of genes encoding stress-response proteins, and three of the other targets, ppiD, osmY and sucC, are proteins of the latter type. The DNA damage-inducible helicase dinG was likewise established as a protein target. Aspartate carboxylate functions were identified as the probable Ru binding sites in cspC, ppiD and dinG, and threonine and lysine side chains in osmY and sucC, respectively.
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PMID:Identification of (eta6-arene)ruthenium(II) protein binding sites in E. coli cells by combined multidimensional liquid chromatography and ESI tandem mass spectrometry: specific binding of [(eta6-p-cymene)RuCl2 (DMSO)] to stress-regulated proteins and to helicases. 1751 97

The cold shock response of Escherichia coli is elicited by downshift of temperature from 37 degrees C to 15 degrees C and is characterized by induction of several cold shock proteins, including CsdA, during the acclimation phase. CsdA, a DEAD-box protein, has been proposed to participate in a variety of processes, such as ribosome biogenesis, mRNA decay, translation initiation, and gene regulation. It is not clear which of the functions of CsdA play a role in its essential cold shock function or whether all do, and so far no protein has been shown to complement its function in vivo. Our screening of an E. coli genomic library for an in vivo counterpart of CsdA that can compensate for its absence at low temperature revealed only one protein, RhlE, another DEAD-box RNA helicase. We also observed that although not detected in our genetic screening, two cold shock-inducible proteins, namely, CspA, an RNA chaperone, and RNase R, an exonuclease, can also complement the cold shock function of CsdA. Interestingly, the absence of CsdA and RNase R leads to increased sensitivity of the cells to even moderate temperature downshifts. The correlation between the helicase activity of CsdA and the stability of mRNAs of cold-inducible genes was shown using cspA mRNA, which was significantly stabilized in the DeltacsdA cells, an effect counteracted by overexpression of wild-type CsdA or RNase R but not by that of the helicase-deficient mutant of CsdA. These results suggest that the primary role of CsdA in cold acclimation of cells is in mRNA decay and that its helicase activity is pivotal for promoting degradation of mRNAs stabilized at low temperature.
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PMID:Complementation analysis of the cold-sensitive phenotype of the Escherichia coli csdA deletion strain. 1755 20


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