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Biomedical subjects

S G Hughes

Publications and source records attributed to S G Hughes.

14 recordsLinked to original sources
PubMed1990

The isolation and sequence analysis of two seed-expressed acyl carrier protein genes from Brassica napus.

Genomic Southern blot analysis of Brassica napus DNA indicates that seed-expressed acyl carrier protein (ACP) is encoded by a multigene family of some 35 genes/haploid genome. Two genomic clones encoding B. napus ACP have been isolated and sequenced. The coding sequences of the 2 respective genes were found to be perfectly homologous to 2 distinct B. napus seed-expressed cDNAs and therefore represent seed-expressed forms of ACP. The 2 genomic ACP sequences share 94% homology within their coding sequences. Both genes are interrupted by 3 intervening sequences whose position within the 2 coding sequences is conserved. RNase protection studies were used to map the transcription start site of one of the genes and to provide further evidence that the gene is seed-expressed. The expression of a sub-group of the ACP gene family was found to be developmentally regulated in concert with the storage lipid synthetic phase of seed development. The coding sequence of both B. napus genes are highly homologous (96% and 93% respectively) to a Brassica campestris ACP cDNA sequence, suggesting that they may have evolved from this ancestral gene.

Acyl Carrier Protein↗
PubMed1988

Plastid-localised seed acyl-carrier protein of Brassica napus is encoded by a distinct, nuclear multigene family.

Acyl-carrier protein (ACP) is a key component involved in the regulation of fatty acid biosynthesis in plants. cDNA clones encoding ACP from Brassica napus (oil seed rape) embryos have been isolated using oligonucleotide probes derived from heterologous ACPs. Analysis of the DNA sequence data, in conjunction with N-terminal amino acid sequence data, revealed ACP to be synthesized from nuclear DNA as a precursor containing a 51-amino-acid N-terminal extension. Immunocytochemical studies showed ACP to be localised solely within the plastids of B. napus seed tissue and it would therefore appear that the N-terminal extension functions as a transit peptide to direct ACP into these organelles. Analysis of several cDNA clones revealed sequence heterogeneity and thus evidence for an ACP multigene family. From ten cDNA clones, six unique genes, encoding five different mature ACP polypeptides, were identified. Northern blot hybridisation studies provide evidence that the seed and leaf forms of rape ACP are encoded by structurally distinct gene sets.

Acyl Carrier Protein↗
PubMed1987

Molecular cloning and sequence analysis of complementary DNA encoding rat mammary gland medium-chain S-acyl fatty acid synthetase thio ester hydrolase.

Poly(A)+ RNA from pregnant rat mammary glands was size-fractionated by sucrose gradient centrifugation, and fractions enriched in medium-chain S-acyl fatty acid synthetase thio ester hydrolase (MCH) were identified by in vitro translation and immunoprecipitation. A cDNA library was constructed, in pBR322, from enriched poly(A)+ RNA and screened with two oligonucleotide probes deduced from rat MCH amino acid sequence data. Cross-hybridizing clones were isolated and found to contain cDNA inserts ranging from approximately 1100 to 1550 base pairs (bp). A 1550-bp cDNA insert, from clone 43H09, was confirmed to encode MCH by hybrid-select translation/immunoprecipitation studies and by comparison of the amino acid sequence deduced from the DNA sequence of the clone to the amino acid sequence of the MCH peptides. Northern blot analysis revealed the size of the MCH mRNA to be 1500 nucleotides, and it is therefore concluded that the 1550-bp insert (including G X C tails) of clone 43H09 represents a full- or near-full-length copy of the MCH gene. The rat MCH sequence is the first reported sequence of a thioesterase from a mammalian source, but comparison of the deduced amino acid sequences of MCH and the recently published mallard duck medium-chain S-acyl fatty acid synthetase thioesterase reveals significant homology. In particular, a seven amino acid sequence containing the proposed active serine of the duck thioesterase is found to be perfectly conserved in rat MCH.

Amino Acid Sequence↗
PubMed1985

Cloning an Aspergillus nidulans developmental gene by transformation.

We have developed a transformation system for Aspergillus nidulans giving a frequency of transformation high enough to screen a gene bank from which we were able to isolate and clone the A. nidulans developmental gene brlA by visual selection. The vector contains the selective marker argB+, and with it a frequency of transformation of 500 stable transformants/micrograms plasmid DNA can regularly be achieved. The evidence suggests that transformation is by integration but spontaneous excision of integrated plasmids is apparently frequent enough to allow the recovery of transforming plasmids in Escherichia coli.

Aspergillus nidulans↗
PubMed1985

Effects of psoralen on replicon size and mean rate of DNA synthesis in partially synchronized cells of Pisum sativum L.

We have examined by fibre autoradiography the spacing of replicons in pea root meristems during synchronized entry into S phase from arrest at the G1/S boundary. Pretreatment with the DNA cross-linking agent, psoralen, produces a marked shortening of replicon spacing, suggesting that premature arrest of the replication fork results in the recruitment of additional initiation points within a given replicon family. This is discussed in relation to models for the control of DNA replication.

Autoradiography↗
PubMed1985

Evaluation of glutamic acid and glycine as sources of nonessential amino acids for lake trout (Salvelinus namaycush) and rainbow trout (Salmo gairdnerii).

A semi-purified test diet which contained either glutamic acid or glycine as the major source of nonessential amino acids (NEAA) was fed to lake and rainbow trout. Trout fed the diet containing glutamic acid consistently showed better growth and feed conversion efficiencies than those fed the diets containing glycine. The data indicate that these trout utilize glutamic acid more efficiently than glycine when no other major sources of NEAA are present.

Animals↗
PubMed1980

The isolation and characterization of a sequence-specific endonuclease from Anabaena subcylindrica.

An endonuclease, AsuI, was isolated from extracts of Anabaena subcylindrica on the basis of gel-electrophoretic analysis of digests of bacteriophage-lambda DNA with the paritally purified extracts. The enzyme requires Mg2+, but no other cofactors. Endonuclease AsuI recognizes the interrupted tetranucleotide sequence: (Formula: see tex), and breaks the phosphodiester bonds indicated by the arrows to leave single-stranded trinucleotide projections at the 5'-termini of the DNA fragments.

Bacteriophage lambda↗
PubMed1980

The nucleotide sequences recognized by endonucleases AvaI and AvaII from Anabaena variabilis.

Determination of the 5'-terminal sequences flanking all the individual cleavage sites for endonuclease AvaI in bacteriophage-lambda DNA has shown that this enzyme recognizes the hexanucleotide sequences: (Formula: see text), This sequence is cut as shown by the arrows to give single-stranded 5'-tetranucleotide protrusions (cohesive ends). Endonucleases SmaI, XhoI and XmaI recognize different symmetrical subsets of this sequence and provide independent evidence for the occurrence of these subsets at particular endonuclease-AvaI cleavage sites in the bacteriophage-lambda genome. Further evidence for this structure came from the demonstration that DNA fragments generated by endonuclease AvaI can be ligated to form a discrete set of larger molecules and from nearest-neighbor analysis which showed that cytosine residues occurred at the 3'-side of cleavage points. The observation that endonuclease AvaII recognized a subset of the sites recognized by AsuI [Hughes, Bruce & Murray (1979) Biochem. J. 185, 59-63[ led to the deduction that AvaII recognize the pentanucleotide sequence: (Formula: see text), and breaks internucleotide bonds at the positions indicated by the arrows.

Bacteriophage lambda↗
PubMed1977

A map of the cleavage sites for endonuclease AvaI in the chromosome of bacteriophage lambda.

The linear order of nine fragments generated by the action of endonuclease AvaI on the DNA of bacteriophage lambda was determined from the altered fragmentation patterns of bacteriophages containing known deletions and of hybrids of bacteriophages lambda and phi80. Digestion of 5'-terminally 32P-labelled bacteriophage-lambda DNA was used to identify the terminal fragments. Measurement of relative fragment lengths permitted rough mapping of the endonuclease-AvaI cleavage sites relative to the ends of the bacteriophage-lambda chromosome. The fragment order was confirmed and the map refined by analysis of the fragmentation of derivative phages containing single cleavage sites for endonuclease EcoRI.

Chromosome Mapping↗
PubMed1976

Isolation and characterization of two sequence-specific endonucleases from Anabaena variabilis.

Two endonucleases, AvaI and AvaII, were isolated from Anabaena variabilis on the basis of their ability to make a limited number of breaks at specific points in bacteriophage lambda DNA. Neither enzyme has cofactor requirements beyond Mg2+. Endonuclease AvaI makes eight breaks in the phage lambda chromosome at which the 5'-terminal sequence is pPy-C-G-N. AvaII endonuclease cuts phage lambda DNA more extensively, yielding fragments with the 5'-terminal sequence G-T-C-N or G-A-C-N. Neither enzyme generates cohesive ends.

Bacteria↗