共查询到20条相似文献,搜索用时 15 毫秒
1.
Summary A novel deletion derivative, kal, of the kalilo senescence plasmid from Neurospora intermedia, was recovered from a culture treated with chloramphenicol. The deletion derivative exists in mitochondria as two different, equally abundant forms: a 2.8 kb duplex DNA molecule kal-2.8) and a 1.4 kb hairpin form kal-1.4). The kal-2.8 plasmid contains the 1366 by terminal inverted repeats and a partially duplicated 102 by segment of the unique sequence of the 8.6 kb kalilo plasmid. In contrast, the kal-1.4 hairpin plasmid appears to result from the folding of single strands that are generated during the replication of kal-2.8. Both forms of kal have covalently linked terminal proteins. Sequence analysis suggests that kal was generated either by slippage of the tip of a growing strand during the replication of kalilo, or by illegitimate recombination between two copies of the plasmid at non-homologous palindromic sequences that might form cruciform structures. In either case, the deletion process was mediated at least in part by an inverted repeat of 5 by in the unique region of kalilo. Since the terminal segments of kalilo DNA that are implicated in plasmid integration might also form cruciform structures, it is possible, but improbable, that the process that generated the first kal molecule is related to that which mediates integration of the plasmid into mitochondrial DNA. 相似文献
2.
Akihiro Kibe Kazunori Shimada Yasuyuki Takagi 《Molecular & general genetics : MGG》1979,168(3):293-298
Summary Hybrid ColE1 plasmids called ColE1-cos-guaA or ColE1-cos-gal can be efficiently transduced into various E. coli K-12 cells through packaging into phage particles. Using these plasmids, repair of ultraviolet-light (UV) damaged ColE1 DNAs was studied in various UV sensitive E. coli K-12 mutants. (1) The host mutations uvrA and uvrB markedly reduced host-cell reactivation of UV-irradiated ColE1-cos-guaA. (2) Pre-existing hybrid ColE1 plasmids had no effect on the frequency of phage-mediated transduction of another differentially marked hybrid ColE1 DNAs. (3) ColE1-cos-guaA and ColE1-cos-gal DNAs could temporarily but not stably co-exist in E. coli K-12 recA cells. (4) The presence of ColE1-cos-gal in uvrB cells promoted the repair of super-infected UV-irradiated ColE1-cos-guaA about 7-fold. (5) The same ColE1-cos-gal plasmid in a uvrB recA double mutant did not have this promoting effect. These results indicate that the effect of resident hybrid ColE1 plasmids is manifested by the host recA
+ gen function(s) and suggest that ColE1 plasmid itself provides no recA
+-like functions. 相似文献
3.
Summary Fragments of the E. coli chromosome that carry the dnaB groPB534 or groPB612 alleles have been cloned into a cosmid vector. The resulting recombinant plasmids contained the genes uvrA, groP (B534 or B612), and lexA. Further subcloning into high copy number plasmids, during which the uvrA and lexA genes were removed successively, yielded a groPB534 and groPB612 DNA fragment of about 2.4 kb each. Both fragments contained an overlapping 1.8 kb segment of DNA in which the sites of all restriction enzymes tested were identical. The size of these dnaB gene fragments were further delimited by deletion analysis.In E. coli groPB534 in which wild-type and A mutants do not replicate (Georgopoulos and Herskowitz 1971) phage replication is rescued if the strain contains the groPB534 gene on high copy number plasmids. On the contrary, in E. coli groPB612, which is temperature-sensitive for its groP character, replication of and A is abolished at 30° C if the strain contains the groPB612 recombinant plasmid. On the other hand, replication of B remains unaffected whether or not the groP strains harbor the isogenic dnaB gene-containing plasmid. The results suggest that within the cell not only the quality but also the relative amounts of dnaB and P protein are crucial for phage replication. 相似文献
4.
Summary The purified bacteriophage replication proteins O and P sediment separately in metrizamide gradients of low ionic strength as dimers. Together they interact with each other forming an oligomer, composed of two molecules of O and one molecule of P. The O-P oligomer is active in the in vitro replication of ori-containing DNA.Equilibrium sedimentation in preformed metrizamide density gradients under conditions that separate DNA-protein complexes from free proteins was employed in order to study possible interactions among the replication proteins and ori DNA. It was found that the P protein binds specifically to ori-containing plasmid DNA only in the presence of O protein. About 100 molecules of O and 10 molecules of P form a complex with the ori DNA. The DNA-O-P complex was shown to be active in an in vitro replication system.Since the physical interactions between ori and O and between P and the Escherichia coli dnaB replication protein are well documented, the evidence for a O-P interaction presented in this paper provides the missing link in the molecular mechanism that enables to direct the host replication machinery to the replication of its own DNA. 相似文献
5.
Summary Temperature sensitive dnaAts46 mutants, in which initiation of chromosome replication is blocked at 42° C, are unable to maintain a dv plasmid at the permissive temperature unless the plasmid carries a mutation in gene P of the type permitting phage to grow in groP (dnaB) bacteria. The growth rate of dnaAts46 mutants seems to be impaired by the presence of the dvP mutant plasmid.Cold sensitive dnaAcos mutants which overinitiate replication at low temperature and grow normally only at 40° and above, can maintain efficiently dvP
+ plasmids as well as dvP mutants. Cold sensitivity of dnaAcos mutants is suppressed by the presence of the plasmid dvP
+ and by certain dvP mutants, but not by others.The gene P product seems to act by reducing the initiation potential of both types of dnaA mutants, aggravating the initiation defect in dnaAts46 and correcting the overinitiation of dnaAcos. 相似文献
6.
Summary Two senscence-specific DNAs (sen-DNAs and ) were tested for their ability to drive autonomous replication in yeast and Podospora. The but not the sequence has autoreplicative (ARS) properties in yeast; the ARS sequences of are not included in the region common to all the sen-DNAs. Neither the nor the sequences can confer autoreplicative properties in Podospora. These sequences inserted into a hybrid vector carrying the suppressor tRNA, su4-1, do not change the mode of transformation of a suppressible leu-1-1 strain of Podospora: the transformation is by integration whether or not the plasmid carries a sen-DNA sequence. The su4-1 gene integrates at its homologous site in a minority of cases. It is possible to reisolate free plasmids at a low frequency from some transformants. The presence of a sen-DNA on the transforming vector has no effect upon the longevity of the transformants. 相似文献
7.
K. G. Hardy G. G. Meynell J. E. Dowman B. G. Spratt 《Molecular & general genetics : MGG》1973,125(3):217-230
Summary Eleven colicin factors have been placed in two groups defined by a number of physiological criteria such as the effect of the host recA (recombination-proficiency) allele on colicin titres and the maximum number of copies of the colicin factor per chromosome. The fundamental difference between the two groups may lie in the molecular weight of the plasmid DNA: one group is about 5x106, the other about 70x106. The colicins specified by members of each group are also related. Colicin factors within the same group may therefore resemble each other because they are descended from the same ancestral plasmid which was either EK-like of low molecular weight or BIV-like of high molecular weight.Aided by grants from the Science Research Council and the Central Research Fund of the University of London. 相似文献
8.
Summary A genetic procedure for selection of specific clones, by homologous recombination between clones from a gene clonotheque and sequences cloned into a plasmid, was developed. Resulting clones are isolated in transduction experiments by plating infected Escherichia coli cells under conditions selecting for the antibiotic resistance marker carried by the plasmid. The feasibility of the method was demonstrated in a model test system as well as by isolation of -interferon-specific sequences from the human gene clonotheque. 相似文献
9.
Masatosi Murai Hideaki Miyashita Hiroyuki Araki Tatsuji Seki Yasuji Oshima 《Molecular & general genetics : MGG》1987,210(1):92-100
Summary The structure of a 1.5-kb DNA sequence that is necessary and sufficient for the replication of an 8.2-kb cryptic plasmid, pFTB14, isolated from a strain of Bacillus amyloliquefaciens has been characterized. The 1.5-kb DNA sequence contains an open reading frame, rep, stretching for 1017 bp, a promoter region for rep expression, and a possible replication origin for the plasmid upstream of the promoter. The rep product is trans-active and essential for plasmid replication. The predicted rep protein is a basic protein, as are the RepC protein of pT181, RepB of pUB110 and protein A of pC194 (all these found in staphylococci) and the protein of the R6K plasmid of Escherichia coli. The predicted rep protein has highly homologous amino acid sequences with protein A of pC194 and RepC of pUB110 throughout the protein molecule, but not with RepC of pT181, of R6K or protein RepH encoded by and iniating the replication of pC194. 相似文献
10.
A DNA sequence (8–19T) of 2.3 kilobase pairs (kb) of Drosophila melanogaster was localized by in situ hybridization to the extreme ends of polytene chromosomes and to the chromocenter. The relative abundance of this sequence at the ends of polytene chromosomes X2L2R3L3R is 13.41.902.7. This differential distribution is probably due to different copy numbers at the individual telomeric regions. Restriction enzyme analysis of genomic DNA shows that 8–19T sequences are interspersed with other sequences. The clone 8–19T, which contains most of this interspersed repetitive sequence, is itself not internally repetitive but has a complex sequence composition. Some of these sequences are transcribed into poly(A)+RNA. We suggest that the ends of Drosophila chromosomes are of a complex arrangement with some sequences common to all ends. 相似文献
11.
John W. Little 《Molecular & general genetics : MGG》1979,177(1):13-22
Summary The E. coli recA gene was cloned from the phage precA into the vector pBR313. A plasmid, pJL3, was also isolated by cloning a portion of the recA gene into the vector pBR322. pJL3 coded for a fragment of the recA protein 34 Kd (kilodaltons) in size (compared to 40 Kd for the intact protein). This fragment was antigenically related to the recA protein and its synthesis was subject to the same controls as that of the recA protein. The fragment did not express any detectable recA function. When wild-type cells with pJL3 were treated with nalidixic acid, the 34 Kd fragment and the -lactamase, made from a gene located downstream from the recA segment, were expressed at very high levels. Moreover, in these cells the rate of synthesis of intact recA protein from the chromosome was inhibited about 2-fold, relative to other chromosomal proteins, when compared to wild-type cells with the pBR322 vector. High level expression of the recA protein fragment and/or the -lactamase appeared to be lethal. The size of the 34 Kd fragment, taken together with the location of chain-termination codons in pJL3, localizes the regulatory region of the recA gene within 100 base pairs. 相似文献
12.
Summary Four E. coli Hfr strains, representing stable (Hfr Cavalli), moderately stable (AB312) and unstable (Ra-1, Ra-2) Hfr states, were used in the isolation of a series of F plasmids. Type II Fs were found to be the most prevalent F plasmid formed from all of the Hfrs, while the percentages of tra Fs increased as the stability of the Hfr increased. Two observations suggested that F formation in unstable Hfrs like Ra-2 may proceed through a type II F precursor. First, the major F products of Ra-2 are tra
+ type II Fs and, second, other F types (I, II) and classes (tra
+, tra) from Ra-2 appeared to be deletion derivatives of a larger F progenitor. By monitoring the molecular changes that occur when the Ra-2 derived type II F pWS200 is transferred from one recA host to another, we have found that all F types and classes can be generated from pWS200 in a recA-independent manner. F sequences involved in the genetic conversions of pWS200 include the oriT locus and the directly repeated junctions of F and chromosomal DNA. A model for the formation of Fs in unstable Hfrs is postulated in which a tra
+ type II F primary excision product is seen to be modified, through recA-independent processes, to other F types and classes. This model differs from the current model of F formation in that independent excision events from the Hfr chromosome are not seen as the source of type I and type II Fs.These studies have also shown that the formation of tra Fs is a recA-independent process that can occur from the F and Hfr states, that -mediated deletions in pWS200 often demonstrate regional specificity in having endpoints near the ilv operon and that genetic alterations in either replication origin of pWS200 (F oriV, chromosomal oriC) stabilize the replication of this mini-Hfr cointegrate. 相似文献
13.
Steven R. King Michael A. Krolewski Sandra L. Marvo Paul J. Lipson Kay L. Pogue-Geile Jae Hoon Chung S. Richard Jaskunas 《Molecular & general genetics : MGG》1982,186(4):548-557
Summary The nucleotide sequences involved in the illegitimate recombination of four recombinants between bacteriophage DNA and pBR322 in E. coli (TA6, KA3, TA1R, and KA7) were determined. Each resulted from recombination between regions of homology of 10 to 13 base pairs. The presence of a recA
+ allele was found to stimulate recombination between DNA and pBR322 approximately 10-fold. TA6, KA3, and KA7 were isolated in the presence of a recA
+ allele and therefore, may have been generated by the recA recombination system. However, TA1R was isolated in a recA mutant, and was presumably generated by a different recombination system. The possibility that it was generated by DNA gyrase is discussed. Two recombination events were required to form KA7, which may indicate that it also was generated by DNA gyrase. 相似文献
14.
Prophage lambda induction caused by mini-F plasmid genes 总被引:3,自引:0,他引:3
Summary When bacterial cells harboring a temperaturesensitive replication plasmid, which carries the particular ccd segment of a mini-F plasmid, are transferred to 42°C, cell division is inhibited after incubation for an appropriate time. The inhibition occurs, when the copy number of the plasmid decreases to become critically low, about one per cell (Ogura and Hiraga 1983 b). In phage lysogens carrying this type of plasmid, the prophage is induced in a small portion of the cell population under the same conditions, in addition to the inhibition of cell division in most of cells. The prophage induction, but not the inhibition of normal cell division, depends on normal recA function. Both induction of prophage and inhibition of cell division are suppressed by the simultaneous presence of a replication proficient plasmid carrying the ccdA gene. We discuss molecular mechanisms of the ccd function that couples host cell division to plasmid proliferation and induces the prophage. Additionally, we propose a hypothesis that the ccd mechanism of F plasmid contributes to indirect induction of prophage by an F plasmid damaged by UV-irradiation and then introduced into a lysogen via conjugation.Abbreviations kb
kilobase pairs. m.o.i., multiplicity of infection 相似文献
15.
Summary The region of the phage lambda chromosome containing the attachment site (P · P) and the genes int and xis, excised by the action of endonuclease R.EcoRI, has been inserted into the unique site for that enzyme on the promiscuous conjugative plasmid, RP4, generating the recombinant plasmid RP4att. Transformants containing the hybrid plasmid were recognised by their ability to allow efficient lysogenization by phage b2 (Weil and Signer, 1968; Echols et al., 1968) containing the mutant attachment site · P. The construction and properties of the hybrid plasmid RP4att are described. 相似文献
16.
P. D. S. Caligari Y. M. H. B. Yapabandara E. M. Paul J. Perret P. Roger J. M. Dunwell 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1993,86(7):875-879
Two inbred cultivars of Nicotiana tabacum (tobacco), Samsun and Xanthi, were transformed with the plasmid pBI 121 using Bin 19 in Agrobacterium tumefaciens. The plasmid carries the nptII gene conferring kanamycin resistance and the uidA gene encoding -glucuronidase (GUS). Progeny carrying the genes in the homozygous condition were identified and selfed over several generations. One line homozygous for the introduced genes and one untransformed control from each cultivar were then selected and crossed reciprocally to give four families per cultivar. Seeds from each family were grown in a replicated field trial and all plants scored for a range of morphological and agronomic characters. In addition, leaf samples were taken and GUS activity measured. In the Samsun material, which contained one copy of the introduced gene at a single locus and showed high levels of GUS expression, the transformed homozygote showed twice the level of GUS activity as the hemizygotes, wheareas in the Xanthi line, which had a lower level of GUS, the hemizygotes showed the same level of GUS activity as the transformed homozygote. The agronomic data showed differences between the families, but the source of such differences could not be ascribed unambiguously. The results are discussed in the light of related information on gene expression and field performance from other transgenic material. 相似文献
17.
The efficiency of gene targeting within different segments of genes in yeast was estimated by transforming yeast cells with double-stranded integrative plasmids, bearing functional gene domains [promoter (P), ORF (O) and terminator (T)] derived from the common genetic markers HIS3, LEU2 , TRP1 and URA3. Transformation experiments with circular plasmids carrying a single gene domain demonstrated that the 5 and 3 flanking DNA regions (P and T) of the HIS3 and URA3 genes are preferred as sites for plasmid integration by several fold over the corresponding ORFs. Moreover, when plasmids bearing combinations of two or three regions were linearized to target them to a specific site of integration, three of the ORFs were found to be less preferred as sites for plasmid integration than their corresponding flanking regions. Surprisingly, in up to 50% of the transformants obtained with plasmids that had been linearized within coding sequences, the DNA actually integrated into neighbouring regions. Almost the same frequencies of ORF mis-targeting were obtained with plasmid vectors containing only two functional domains (PO or OT) of the gene URA3, demonstrating that this event is not the consequence of competition between homologous DNA regions distal to the ORF. Therefore, we suggest that coding sequences could be considered to be cold spots for plasmid integration in yeast.Communicated by A. Aguilera 相似文献
18.
G. R. Zealey A. R. Goodey J. R. Piggott M. E. Watson R. C. Cafferkey S. M. Doel B. L. A. Carter A. E. Wheals 《Molecular & general genetics : MGG》1988,211(1):155-159
Summary A 2 m circle-based chimaeric plasmid containing the yeast LEU2 and the Herpes Simplex Virus type 1 thymidine kinase (HSV-1 TK) genes was constructed. Transformants grown under selective conditions for the LEU2 gene harboured the plasmid at about 15 copies per cell whilst selection for the HSV-1 TK gene led to an increase to about 100 copies per cell. Furthermore, the plasmid copy number could be controlled by the stringency of selection for the TK gene, and the increase in TK gene dosage was reflected in an increase in intracellular thymidine kinase activity. The mitotic stability of the plasmid in high-copy and low-copy number cells was determined. High-copy number cells showed a greater mitotic stability. The relationship of TK expression to plasmid copy number may be useful for the isolation of plasmid copy number mutants in yeast and the control of heterologous gene expression. 相似文献
19.
Toyoaki Tenzen Yohko Matsuda Hisako Ohtsubo Eiichi Ohtsubo 《Molecular & general genetics : MGG》1994,245(4):441-448
Tnr1 is a repetitive sequence in rice with several features characteristic of a transposable DNA element. Its copy number was estimated to be about 3500 per haploid genome by slot-blot hybridization. We have isolated six members of Tnr1 located at different loci by PCR (polymerase chain reaction) and determined their nucleotide sequences. The Tnr1 elements were similar in size and highly homologous (about 85%) to the Tnr1 sequence identified first in the Waxy gene in Oryza glaberrima. A consensus sequence of 235 by could be derived from the nucleotide sequences of all the Tnr1 members. The consensus sequence showed that base substitutions occurred frequently in Tnr1 by transition, and that Tnr1 has terminal inverted repeat sequences of 75 bp. Almost all the chromosomal sequences that flank the Tnr1 members were 5-PuTA-3 and 5-TAPy-3, indicating that Tnr1 transposed to 5-PuTAPy-3 sites, duplicating the TA sequence. PCR-amplified fragments from some rice species did not contain the Tnr1 members at corresponding loci. Comparison of nucleotide sequences of the fragments with or without a Tnr1 member confirmed preferential transposition of Tnr1 to 5-PuTAPy-3 sites, duplicating the TA sequence. One amplified sequence suggested that imprecise excision had occurred to remove a DNA segment containing a Tnr1 member and its neighboring sequences at the Waxy locus of rice species with genome types other than AA. We also present data that may suggest that Tnr1 is a defective form of an autonomous transposable element. 相似文献
20.
Summary Lambda prophage in auxotrophic lysogens can be induced by omission of one or combinations of the required amino acids from the culture medium. Such amino acid deprivation can result in nearly as effective induction of lambda as thymine deprivation. Prophage 424 is also induced equally effectively under both conditions although to a lesser extent than lambda. By contrast prophage 21 and i21 are differentially induced effectively by thymine deprivation and virtually not at all during amino acid deprivation. The same differential induction of 21 and equivalent induction of and 424 occur when all three prophages are present in the same lysogen. Increasing the levels of repressor with a cI carrying-plasmid prevented amino acidless induction of as did the ind
– mutation. A recA, but not a recB, mutation in the host prevented induction by amino acid deprivation. A recC mutant host showed increased spontaneous induction of and 21 prophages. The findings reported are used as an argument that the recA protease probably is not itself acting as the inducing protease and that a likely source of the observed specificity is an effector molecule. Different effector molecules may be produced in response to different exigent situations, to which the phage repressors may have evolved sensitivity. i80 was inducible both by amino acid and thymine deprivation. 相似文献