Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.30.2 (endonuclease)
18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The most distal 300 kb of human chromosome 21q was cloned and mapped using telomeric yeast artificial chromosomes (YACs). The region contains low-copy subtelomeric repeats at the telomeric end, chromosome 21-specific sequences more centromerically, and the S100B gene at a distance of 100-140 kb from the chromosome terminus. RecA-assisted restriction endonuclease cleavage of genomic DNA showed that the cloned fragments correspond to telomere-terminal genomic DNA, and restriction enzyme mapping of the YACs shows that the smaller clone (175 kb) corresponds exactly to the telomeric end of the larger one (300 kb). PCR assays for 21q-specific markers were used to show that COL6A1, COL6A2, and LA161 were all outside of the subtelomeric region spanned by the YACs and thus at least 300 kb from the 21q terminus. The molecular probes provide telomeric closure for existing 21q maps.
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PMID:Structure of the terminal 300 kb of DNA from human chromosome 21q. 778 83

Using the method of polymorphisms of lengths of restriction fragments (RFLP), the authors compare agreement and differences in the normal healthy Czech population and in families with a patient suffering from Down's syndrome. 2-alpha-satellite DNA probes were used which are weighed in the pericentromeric area of heterochromatin of the long arms of chromosomes 13 and 21. These probes contain a number of repetitive sequences, most frequently represented in human heterochromatin of the majority of chromosomes. By hybridization with an alpha-RI-6 probe multiallelic polymorphisms were obtained in families with Down's syndrome in five restrictive endonucleases (Bsp RI, Eco RI, Pst I, Taq I and Xba I). Restrictions with enzymes Bam HI and Hind III were non-polymorphous. Hybridization with the alpha-RI-IB probe revealed polymorphism with restrictive endonuclease Taq I. Enzymes Bam HI, Eco RI, Hind III, Pst I and Xba I (3) were non-polymorphous. The difference of the two probes in the centromeric area of chromosomes 13 and 21 was confirmed by hybridization in situ, using 3H-labelled thymidine triphosphate (TIP) in quantitative experiments on short-term cultures of lymphocytes of healthy subjects (4).
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PMID:[Restriction fragment length polymorphisms in the families of patients with Down's syndrome (trisomy 21)]. 790 97

Irradiation in the G1 phase of the cell cycle delays the onset of DNA synthesis and transiently inhibits the activation of replication origins in mammalian cells. It has been suggested that this inhibition is the result of the loss of torsional tension in the DNA after it has been damaged. Because irradiation causes DNA damage at an undefined number of nonspecific sites in the genome, it is not known how cells respond to limited DNA damage, and how replication origins in the immediate vicinity of a damage site would behave. Using the sequence-specific HO endonuclease, we have created a defined double-stranded DNA break in a centromeric plasmid in G1-arrested cells of the yeast Saccharomyces cerevisiae. We show that replication does initiate at the origin on the cut plasmid, and that the plasmid replicates early in the S phase after linearization in vivo. These observations suggest that relaxation of a supercoiled DNA domain in yeast need not inactivate replication origins within that domain. Furthermore, these observations rule out the possibility that the late replication context associated with chromosomal termini is a consequence of DNA ends.
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PMID:Activation of a yeast replication origin near a double-stranded DNA break. 792 50

Three DNA hypomethylation mutants of the flowering plant Arabidopsis thaliana were isolated by screening mutagenized populations for plants containing centromeric repetitive DNA arrays susceptible to digestion by a restriction endonuclease that was sensitive to methylated cytosines. The mutations are recessive, and at least two are alleles of a single locus, designated DDM1 (for decrease in DNA methylation). Amounts of 5-methylcytosine were reduced over 70 percent in ddm1 mutants. Despite this reduction in DNA methylation levels, ddm1 mutants developed normally and exhibited no striking morphological phenotypes. However, the ddm1 mutations are associated with a segregation distortion phenotype. The ddm1 mutations were used to demonstrate that de novo DNA methylation in vivo is slow.
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PMID:Arabidopsis thaliana DNA methylation mutants. 831 32

A study on the factors involved in chromosome digestion by restriction endonuclease was carried out on 5-azacytidine treated and untreated human chromosomes 1, 9, 15 and 16 by using NdeII and Sau3AI isoschizomers. After treatment with 5-azacytidine, chromosomes 1, 9, 15, and 16 showed two differentiated areas at the centromeric regions: the centromere, fully condensed, and the pericentromeric heterochromatin, decondensed. Chromosomes not treated with 5-azacytidine after digestion with Sau3AI and NdeII showed all the centromeric regions undigested, except pair number 1, digested at the pericentromeric area. Digestion of the 5-azacytidine decondensed chromosomes with Sau3AI and NdeII showed the centromeres undigested in the four chromosome pairs while the pericentromeric heterochromatin appeared largely digested. Other factors, different to target distribution, are necessary to explain the pattern of restriction endonuclease digestion observed in this communication.
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PMID:Differential digestion of the centromeric heterochromatic regions of the 5-azacytidine-decondensed human chromosomes 1, 9, 15, and 16 by NdeII and Sau3AI restriction endonucleases. 852 63

The chromosomes of lake trout (Salvelinus namaycush) contain a considerable amount of heterochromatin located at the centromeres and/or telomeres of several chromosomes, including a sex-specific block located distally on the X chromosome. In order to investigate further the repetitive DNAs of lake trout, genomic DNA from a female was size fractionated (<600 bp) with the restriction endonuclease AluI and fragments were cloned into the bacteriophage M13. A total of 42 clones were isolated. Relative copy number of individual inserts within the lake trout genome was estimated by Southern analysis. Twelve clones were determined to be highly repetitive and were chosen for further investigation. Inserts of these clones contained sequences similar to the AluI/RsaI, EcoRI/DraI, DraI/BstEII, and MboI/BglII families reported from Arctic char (Salvelinus alpinus). The chromosomal location of several of these fragments was determined in lake trout by fluorescence in situ hybridization (FISH). Two related AluI/RsaI sequences (Type A, approximately 140 bp, and Type B,approximately 120 bp) showed differential hybridization. Type A hybridized to the centromeres of all metacentric as well as several acrocentric chromosomes. Type B hybridized to the centromeres of most acrocentric chromosomes. A sequence with homology to the EcoRI/DraI family hybridized to the centromeres of several acrocentric chromosomes. Sequences with partial similarity to the DraI/BstEII family hybridized to the major rDNA sites (nucleolar organizer regions, NORs) and several minor telomeric sites. The interstitial and telomeric heterochromatin of lake trout, including that of the X chromosome, appears to comprise sequences belonging to the MboI/BglII family.
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PMID:Molecular characterization and cytogenetic analysis of highly repeated DNAs of lake trout, Salvelinus namaycush. 856

Hybrid water frogs Rana esculenta reproduce by hybridogenesis: one parental genome (of Rana lessonae) is excluded in the germ line, the other (of Rana ridibunda) is clonally transmitted to haploid gametes. The two parental species differ in that the amount of centromeric heterochromatin revealed by differential staining is much higher in Rana ridibunda. An abundant, tandemly arrayed, centromeric satellite DNA, designated RrS1, is revealed in Rana ridibunda genomes by the restriction endonuclease Stul, which generates a major repetitive sequence fragment of 300 and a minor one of 200 bp. This AT-rich (68%) satellite family is located at the centromeres of the five largest chromosomes (1-5) and of a medium to small heterobrachial one (8 or 9); it thus constitutes only part of the centromeric heterochromatin that characterizes all Rana ridibunda chromosomes. RrS1 represents about 2.5% of the genome of Rana ridibunda; it may represent as little as 0.2% of the genome of Rana lessonae, and cannot be detected in Xenopus laevis frogs or Salamandra salamandra and Triturus carnifex salamanders. Segments of the satellite sequence are similar to sequences of yeast centromeric DNA element CDEIII and of the mammalian CENP-B box. A role for RrS1 and other centromeric satellite DNAs in the germ line genome exclusion of the hybridogenetic frog hybrids, although suggested, has not yet been demonstrated.
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PMID:Molecular characterization of a centromeric satellite DNA in the hemiclonal hybrid frog Rana esculenta and its parental species. 858 3

Large terminal fragments of human chromosomes 2p, 6p, 8q, 12q, and 18q were cloned using yeast artificial chromosomes (YACs). RecA-assisted restriction endonuclease (RARE) cleavage analysis of genomic DNA samples from II unrelated individuals using YAC-derived probes confirmed the telomeric localizations of the half-YACs studied. The cloned fragments provide telomeric closure of maps for the respective chromosome arms and will supply the reagents needed for analyzing and sequencing these distal subtelomeric regions.
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PMID:Molecular cloning and RARE cleavage mapping of human 2p, 6q, 8q, 12q, and 18q telomeres. 859 10

Human chromosomal DNA contains many repeats which might provide opportunities for DNA repair. We have examined the consequences of a single double-strand break (DSB) within a 360-kb dispensable yeast artificial chromosome (YAC) containing human DNA (YAC12). An Alu-URA3-YZ sequence was targeted to several Alu sites within the YAC in strains of the yeast Saccharomyces cerevisiae; the strains contained a galactose-inducible HO endonuclease that cut the YAC at the YZ site. The presence of a DSB in most YACs led to deletion of the URA3 cassette, with retention of the telomeric markers, through recombination between surrounding Alus. For two YACs, the DSBs were not repaired and there was a G2 delay associated with the persistent DSBs. The presence of persistent DSBs resulted in cell death even though the YACs were dispensable. Among the survivors of the persistent DSBs, most had lost the YAC. By a pullback procedure, cell death was observed to begin at least 6 h after induction of a break. For YACs in which the DSB was rapidly repaired, the breaks did not cause cell cycle delay or lead to cell death. These results are consistent with our previous conclusion that a persistent DSB in a plasmid (YZ-CEN) also caused lethality (C. B. Bennett, A. L. Lewis, K. K. Baldwin, and M. A. Resnick, Proc. Natl. Acad. Sci. USA 90:5613-5617, 1993). However, a break in the YZ-CEN plasmid did not induce lethality in the strain (CBY) background used in the present study. The differences in survival levels appear to be due to the rapid degradation of the plasmid in the CBY strain. We, therefore, propose that for a DSB to cause cell cycle delay and death by means other than the loss of essential genetic material, it must remain unrepaired and be long-lived.
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PMID:A double-strand break within a yeast artificial chromosome (YAC) containing human DNA can result in YAC loss, deletion or cell lethality. 875 42

The CMT1A-REP repeat on chromosome 17p11.2-12 is proposed to mediate misalignment and meiotic unequal crossover leading to a 1.5 Mb pair duplication associated with Charcot-Marie-Tooth neuropathy type 1A (CMT1A) and a reciprocal deletion associated with hereditary neuropathy with liability to pressure palsies (HNPP). Restriction enzyme endonuclease mapping indicated that the size of the CMT1A-REP repeat is approximately 24 kb and DNA sequence analysis determined that the repeat is flanked by inverted Alu sequences. Full length Alu sequences are present at the centromeric ends of the proximal and distal CMT1A-REP repeats and at the telomeric end of the distal repeat. A truncated Alu sequence is present at the telomeric end of the proximal repeat suggesting that the distal CMT1A-REP repeat is the progenitor copy. The crossover breakpoints for a series of unrelated CMT1A and HNPP patients were mapped using a variant SacI site found only in the proximal CMT1A-REP repeat. Seventy-six percent (66/85) of patients had breakpoints which mapped to a 3.2 kb interval, providing further evidence for a recombinational hotspot within the CMT1A-REP repeat. A mariner-like element was mapped within the CMT1A-REP repeat approximately 700 bp centromeric to the 3.2 kb interval containing the hotspot. Analysis of this sequence suggested that it does not encode a functional transposon. By Northern blot analysis a cloned fragment from the CMT1A-REP repeat containing the mariner-like sequence detected a 2.2 kb transcript only in testis. Two cDNA clones which contain the mariner-like element were isolated from a human testis cDNA library. These clones which are interrupted by Alu and other repeats appear to be non-functional versions of the transposon. The functional relationship of the mariner-like element to the recombinational hotspot remains unknown. The origin of the CMT1A-REP repeat was investigated through an analysis of homologous sequences in non-human primates. Southern blot analysis indicated that the chimpanzee has two copies of a CMT1A-REP-like sequence, whereas gorilla, orangutan, and gibbon have a single copy. A high degree of conservation amongst non-human primates for restriction fragments specific to the human distal CMT1A-REP repeat provides further evidence that the distal repeat is the progenitor copy. The mariner-like sequence was detected in association with the CMT1A-REP sequence in all primates studied suggesting that the mariner-like element was introduced into the progenitor CMT1A-REP sequence prior to emergence of the proximal and distal CMT1A-REP repeats. These observations suggest that CMT1A-REP sequence appeared as a repeat before the divergence of chimpanzee and human, but after gorilla and human around 6 to 7 million years ago.
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PMID:Primate origin of the CMT1A-REP repeat and analysis of a putative transposon-associated recombinational hotspot. 877 88


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