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Biomedical subjects

N A Straus

Publications and source records attributed to N A Straus.

At least 37 records · Page 2Linked to original sources
PubMed1986

Isolation and nucleotide sequence analysis of the ferredoxin I gene from the cyanobacterium Anacystis nidulans R2.

Two mixed oligonucleotide probes derived from conserved regions of the Synechocystis sp. strain PCC 6714 ferredoxin amino acid sequence were utilized to isolate an Anacystis nidulans R2 clone containing the ferredoxin I gene. Nucleotide sequence analysis revealed a 297-base-pair (bp) open reading frame with a deduced amino acid sequence having high homology to other cyanobacterial ferredoxins. Assuming proteolytic cleavage of the initial methionine residue, the molecular weight of the mature A. nidulans R2 ferredoxin was 10,370. The initial methionine residue was preceded by a probable ribosome-binding site sequence, AGGA. Northern hybridization analysis with the cloned ferredoxin gene indicated an RNA transcript of approximately 450 bp. S1 nuclease mapping localized the transcription start site to a position 64 bases upstream from the initial methionine residue. The nucleotide sequence 14 to 8 bp preceding the transcription start site resembled a typical Escherichia coli promoter, but the sequence in the -35 region did not. Southern hybridization detected only a single copy of the ferredoxin sequence in the A. nidulans R2 genome.

Amino Acid Sequence↗
PubMed1985

Alternariol, a dibenzopyrone mycotoxin of Alternaria spp., is a new photosensitizing and DNA cross-linking agent.

The mycotoxin alternariol (3,4',5-trihydroxy-6'-methyldibenzo [a] pyrone) but not alternariol monomethyl ether (3,4'-dihydroxy-5-methoxy-6'-methyldibenzo [a] pyrone) is phototoxic to Escherichia coli in the presence of near UV light (320-400 nm). The phototoxicity bioassays with a DNA repair-deficient mutant of E. coli suggested that DNA may be the molecular target for photo-induced toxicity of alternariol. Interactions between alternariol and double-stranded, supercoiled DNA suggest that alternariol interacts with DNA by intercalation. No DNA breakage was detected in this system; however, alternariol forms a complex and cross-links double-stranded DNA in near UV light. These results suggest that alternariol is a new phototoxic, DNA-intercalating agent and is a DNA cross-linking mycotoxin in near UV light.

Chemical Phenomena↗
PubMed1983

DNA sequence organization and transcription of the chicken genome.

A new approach has been used to examine DNA sequence organization in the chicken genome. The interspersion pattern was determined by studying the fraction of labelled DNA fragments of different lengths that hybridized to an excess of short chicken repeated DNA sequences. The results indicate that chicken DNA has a pattern of sequence organization quite different than the standard 'Xenopus' or 'Drosophila' patterns. Two classes of unique sequences are found. One, 34% of the genome, consists of unique sequences approx. 4 kb long interspersed with repeated sequences. The second, non-interspersed fraction, 38% of the genome, consists of unique sequences found in long tracts, a minimum of approx. 22 kb in length. In an attempt to determine whether a relationship exists between DNA sequence organization and the distribution of structural genes we have isolated chicken DNA sequences belonging to different interspersion classes and tested each for the presence of structural genes by hybridization to excess poly(A)+ mRNA. Sequences complementary to poly(A)+ mRNA can be found with approximately the same frequency in both the non-interspersed fraction of the genome and a repeat-contiguous fraction enriched for interspersed sequences.

Animals↗
PubMed1983

Sequences complementary to cellular deoxypolypyrimidines are localized in the 3' end of L-cell mRNA.

Many eukaryotic genomes have been shown to contain long pyrimidine tracts. In mouse L-cells, at least some of these pyrimidine tracts are transcribed and form a significant portion of the poly(A)+ RNA sequences. In this study the results from three different experimental methods indicate that the sequences complementary to polypyrimidines are localized to the 3' end of mRNA molecules. First, polypyrimidines reacted preferentially with the 3'-end fragments of mRNA generated by limited alkaline cleavage. Second, digestion of [3H]mRNA-polypyrimidine hybrids with RNase H released 3'-end fragments of mRNA which averaged only 250 nucleotides (NT) in length. Third, polypyrimidine tracts were isolated from cDNA which averaged only 200-250 NT extending from the 3' end of the corresponding mRNAs. These data suggest that the sequences transcribed from pyrimidine tracts are quite close to the 3' end of the cellular messages in which they occur, probably within the terminal untranslated region.

Animals↗
PubMed1982

Repeated sequences in L-cell mRNA complementary to long deoxypolypyrimidines.

Long pyrimidine tracts form part of the repeated DNA sequences in eukaryotic genomes and are among the most highly conserved sequences in evolution. At least some of these sequences are transcribed in L-cells, since they are capable of hybridizing extensively with total cellular RNA. In saturation hybridization experiments involving fractionated cellular RNA, polypyrimidines react preferentially with the polysomal poly(A+) RNA and the nuclear poly (A+) RNA fractions; there is little or no reaction with poly (A-) RNA or with synthetic poly (A). In addition, hybridization between mRNAs and deoxypolypyrimidines is not affected by enzymatic removal of the poly (A+) tract from mRNA molecules. Saturation hybridization experiments indicate that about 1% of mRNA consists of regions complementary to deoxypolypyrimidines. The size of the polypurine regions in mRNA has been measured by gel electrophoresis of RNAase-resistant hybrids and was found to be heterogeneous with an average size of about 35 nucleotides. It is estimated that about half of poly (A-) mRNA molecules in L-cells contain sequences complementary to deoxypolypyrimidines. Although the function of polypyrimidine tracts is not yet known, the conservation and transcription of these sequences suggests an important role in the expression of eukaryotic genes.

Animals↗
PubMed1979

Characterization of the genome of the free-living nematode Panagrellus silusiae: absence of short period interspersion.

The complexity of the DNA of the free-living nematode Panagrellus silusiae has been examined. Reassociation kinetics of pressure-sheared fragments (approximately 290 nucleotides) in 0.18 M Na+ at 60 degrees C showed the presence of foldback, repetitive, and unique DNA sequence elements. The three classes comprise 9.3%, 26.1%, and 61.3% of the total DNA, respectively. The mean length of the foldback duplex DNA after digestion with S1 nuclease is about 185 nucleotides. There are about 1.8 x10(4) inverted repeats per genome. Sequence arrangement was deduced from (1) renaturation kinetic profiles of long and short fragments on hydroxylapatite; (2) the pattern of renaturation of tracer DNA, labeled in vitro with 125I, of various sizes after incubation with excess short fragments; and (3) thermal denaturation behavior of DNA that had been reassociated to various C0t values. It was found that DNA fragments of the repetitive fraction that are, at least, 2000 nucleotides in length are virtually free of unique sequences. Moreover, it is estimated that the repeated segments in this species could extend for 10,000 nucleotide pairs. Thus, Panagrellus DNA lacks the pattern of extensive short period interspersion that is typified by the DNA of Xenopus.

Animals↗
PubMed1978

DNA-sequence organization in the genome of the domestic chicken (Gallus domesticus).

The sequence organization in the DNA of chicken (Gallus domesticus) was studied using hydroxyapatite-monitored reassociation kinetics. DNA 320-nucleotides long reassociates as though it is composed of three components, i.e., a very rapidly reacting fold-back fraction, a component composed of sequences repeated an average of 640 times in the genome, and a large unique fraction representing about 80% of the genome. The sizes of the fold back and repeated components increase only moderately with large increases in fragment size, indicating that these sequences are not extensively interspersed in the genome. Even at a fragment size of 4500 nucleotides, the unique component represents 68% of the DNA. Thus, the chicken genome is not organized in the short-period (Xenopus) interspersion pattern described for a large number of other organisms; rather, the DNA-sequence organization of this vertebrate bears more resemblance to the long-period interspersion pattern of Drosophila.

Animals↗
PubMed1976

Polypyrimidine sequences found in eukaryotic DNA have been conserved during evolution.

L-cell DNA contains an unexpectedly large amount of long pyrimidine tracts. Hydroxyapatite chromatography has been employed to show that these polypyrimidines hydridize extensively to the reiterated DNA of a large number of eukaryotes but fail to hybridize to prokaryotic DNA. This reaction is sequence specific and not the result of a special property of polypyrimidines since random 3H-labelled poly(dC-dT) shows poor hybridization to eukaryotic DNA. The hybrids formed by L-cell polypyrimidines and heterologous repeated sequences have a higher thermal stability than the corresponding hybrids of total repeated DNA indicating that sequences related to these polypyrimidines have been conserved during evolution. Furthermore, at least some of these tracts are transcribed because they are capable of reacting extensively with total cellular RNA. Although the function of these sequences is not yet known, the fact that they are widely conserved in evolution and also transcribed leads us to speculate that they play an an important role in eukaryotic cells.

Biological Evolution↗
PubMed1975

DNA: DNA hybridization studies in black flies.

The phylogenetic relationships of six species of black flies were investigated using the hybridization of iodinated unique DNA sequences. The thermal stability of these labelled hybrids allowed the construction of a phylogenetic tree based on base mismatch between chains of the heterologous duplex.

DNA↗
PubMed1975

Characterization of polypyrimidines in Drosophila and L-cell DNA.

Unusually long pyrimidine tracts (polypyrimidines), ranging from 100 to over 1000 nucleotides in length, have been found in Drosophila melanogaster DNA. They are compared to shorter pyrimidine tracts (25-150 nucleotides) which have previously been found in L-cell DNA. Both species were able to anneal to homologous DNA; Drosophila polypyrimidines formed stable hybrids while L-cell polypyrimidines formed hybrids of lower thermal stability. In both cases, the kinetics of the reaction was rapid, suggesting that these tracts are part of highly repeated DNA.

Animals↗
PubMed1975

DNA from eukaryotic cells contains unusually long pyrimidine sequences.

Analysis of DNA samples from several different organisms revealed the presence of unexpectedly long pyrimidine tracts (polypyrimidine), ranging in size from about 25 to 200 nucleotides in length. This fraction of the DNA accounted for 0.07-0.8 percent of the total thymidine residues. Pyrimidine clusters of this length and amount would not be expected on a random basis, suggesting they may have been conserved during evolution because they are required for a specialized function(s).

Animals↗
PubMed1974

Long pyrimidine tracts of L-cell DNA: localization to repeated DNA.

Like HeLa DNA, L-cell DNA contains a significant number of unexpectedly long pyrimidine tracts. 1.3% of the thymidine residues of L-cell DNA are found in these long polypyrimidine tracts. Analysis of L-cell DNA fractions with different rates of reassociation indicates that polypyrimidine tracts are associated with "repeated" DNA. Longer pyrimidine tracts appear to have a higher repetition frequency than shorter tracts, and some may be repeated as many as 5 x 10(4) times in L-cell DNA.

Animals↗
PubMed1973

Relatedness of mouse satellite deoxyribonucleic acid to deoxyribonucleic acid of various Mus species.

Mouse (Mus musculus musculus) satellite DNA is able to reassociate with repeated DNA sequences of Mus caroli and Mus cervicolor, but low thermal stability of the products indicates significant differences between satellite and related DNAs of these two Mus species. There appear to be several satellite-related populations in M. caroli DNA, each of which forms hybrids of low thermal stability with repeated sequences of M. cervicolor DNA. DNAs from the subspecies Mus musculus molossinus and Mus musculus castaneus reassociate with mouse satellite to form hybrids of very high thermal stability, but the satellite content of M. m. musculus DNA is only about 60% that of M. m. musculus DNA. Reassociation of M. m. musculus nonrepeated DNA with M. m. molossinus DNA reveals no detectable differences between them; reassociation with M. caroli (or M. cervicolor) DNA yields a product whose melting temperature depression relative to homologous DNA is about 5 degrees .

Animals↗
PubMed1973

Analysis of long pyrimidine polynucleotides in HeLa cell nuclear DNA: absence of polydeoxythymidylate.

HeLa cell nuclear DNA contains an unexpectedly large amount of long pyrimidine polynucleotides. These sequences were detected in DNA labeled with [(3)H] thymidine by treatment with formic acid-diphenylamine and subsequent analysis by polyacrylamide gel electrophoresis. About 0.5% of the total thymine residues were found in polynucleotides that migrated more slowly than 4S RNA. No polynucleotides of comparable size were detected in Escherichia coli DNA. The pyrimidine polynucleotides contained no pure poly(dT) sequences (less than 0.0015% of the total residues), as judged by thermal chromatography of a complex formed with poly(A).

Chromatography↗