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J R de Wet

Publications and source records attributed to J R de Wet.

11 recordsLinked to original sources

Visual assays of transformation in plant cells.

We discuss the utility of visual assays for the expression of genes introduced into plant cells. Such assays are valuable for both transient and stable gene expression studies. We review the properties of three visual assays that are already in use or under development phase for maize and other cereal crops. These assays depend on the expression of beta-galactosidase, luciferase, or structural genes required for anthocyanin pigment biosynthesis.

Anthocyanins↗

Firefly luciferase gene: structure and expression in mammalian cells.

The nucleotide sequence of the luciferase gene from the firefly Photinus pyralis was determined from the analysis of cDNA and genomic clones. The gene contains six introns, all less than 60 bases in length. The 5' end of the luciferase mRNA was determined by both S1 nuclease analysis and primer extension. Although the luciferase cDNA clone lacked the six N-terminal codons of the open reading frame, we were able to reconstruct the equivalent of a full-length cDNA using the genomic clone as a source of the missing 5' sequence. The full-length, intronless luciferase gene was inserted into mammalian expression vectors and introduced into monkey (CV-1) cells in which enzymatically active firefly luciferase was transiently expressed. In addition, cell lines stably expressing firefly luciferase were isolated. Deleting a portion of the 5'-untranslated region of the luciferase gene removed an upstream initiation (AUG) codon and resulted in a twofold increase in the level of luciferase expression. The ability of the full-length luciferase gene to activate cryptic or enhancerless promoters was also greatly reduced or eliminated by this 5' deletion. Assaying the expression of luciferase provides a rapid and inexpensive method for monitoring promoter activity. Depending on the instrumentation employed to detect luciferase activity, we estimate this assay to be from 30- to 1,000-fold more sensitive than assaying chloramphenicol acetyltransferase expression.

Animals↗

Molecular biology of the alpha-L-fucosidase gene and fucosidosis.

Human alpha-L-fucosidase, a lysosomal enzyme, hydrolyzes alpha-L-fucose from glycolipids and glycoproteins. Its activity is deficient in human fucosidosis an autosomal recessive disease. In order to understand the molecular basis of this lysosomal storage disorder we have cloned several cDNAs coding for human alpha-L-fucosidase from a human hepatoma and a human liver cDNA library constructed in lambda gt11. Compiling the cDNA sequences of these clones we have identified 1,829 base pairs (bp) encoding human alpha-L-fucosidase. This includes an open reading frame of 1,172 bp, a consensus polyadenylation signal AAT AAA and a poly(A)+ tail. The sequence is incomplete at the 5'-end, and clones encoding the amino terminus of the native protein, the propeptide and leader signal have not yet been isolated. The open reading frame encodes for 390 amino acids with a calculated Mr of 45,557. This represents 78-95% of the mature processed alpha-L-fucosidase. The availability of these cDNA clones has enabled us to map the structural gene for alpha-L-fucosidase to chromosome 1p34.1-1p36.1 by Southern blot analysis of DNA from human-rodent somatic cell hybrids and by in situ hybridization. Furthermore, a Pvu II restriction fragment length polymorphism (RFLP) has been identified at the human alpha-L-fucosidase gene locus. Analysis of mRNA by Northern blotting gives a major species of 2.25 kb. In 4 patients with fucosidosis no mRNA signal was detected and Western blots gave no immunoreactive enzyme. Southern blotting after Eco RI digestion in two fucosidosis families revealed a banding abnormality (extra 6-kb band).(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

Cloning of firefly luciferase cDNA and the expression of active luciferase in Escherichia coli.

A cDNA library was constructed from firefly (Photinus pyralis) lantern poly(A)+ RNA, using the Escherichia coli expression vector lambda gt11. The library was screened with anti-P. pyralis luciferase (Photinus luciferin:oxygen 4-oxidoreductase, EC 1.13.12.7) antibody, and several cDNA clones expressing luciferase antigens were isolated. One clone, lambda Luc1, contained 1.5 kilobase pairs of cDNA that hybridized to a 1.9- to 2.0-kilobase band on a nitrocellulose blot of electrophoretically fractionated lantern RNA. Hybridization of the cloned cDNA to lantern poly(A)+ RNA selected an RNA that directed the in vitro synthesis of a single polypeptide. This polypeptide comigrated with luciferase on NaDodSO4/PAGE and produced bioluminescence upon the addition of luciferin and ATP. A 1.8-kilobase-pair cDNA was isolated by probing the firefly cDNA library with the cDNA from lambda Luc1. This cDNA contained sufficient coding information to direct the synthesis of active firefly luciferase in E. coli.

Animals↗

Molecular cloning of a cDNA for human alpha-L-fucosidase.

A lambda gt11 human hepatoma cDNA expression library was screened with antibodies to human alpha-L-fucosidase, a lysosomal enzyme whose activity is deficient in the human autosomal recessive disease fucosidosis. Three positive clones were identified after screening 9 X 10(6) plaques. One of these was sequenced and found to be spurious, probably representing an out-of-frame cDNA that gave rise to amino acid sequences of unknown length that crossreacted with alpha-L-fucosidase. A second clone, lambda AF3, was isolated which, after establishment in Escherichia coli BNN103, gave rise to a fusion protein of Mr 154,000 containing a human fragment of Mr 40,000 that represented 80% of the mature processed enzyme (Mr 50,000). Southern blot analysis of mouse and human chromosomal DNA confirmed the human origin of insert AF3. The nucleotide sequence of AF3 was determined and colinearity was established between 270 nucleotides and 90 amino acids in alpha-L-fucosidase. AF3 was found to contain 1058 base pairs and to code for 347 amino acids of alpha-L-fucosidase. Four potential glycosylation sites were identified. The frequency of lambda AF3 in the hepatoma library was 0.0018%.

Amino Acid Sequence↗

Synthesis of active firefly luciferase by in vitro translation of RNA obtained from adult lanterns.

Poly (A)+ RNA was isolated from the lanterns of adult fireflies, Photinus pyralis. The Poly (A)+ RNA was translated in a cell-free translation mixture from rabbit reticulocytes and the synthesis of enzymatically active firefly luciferase was demonstrated. The translation products were immunoprecipitated with anti-luciferase and then subjected to SDS gel electrophoresis. It was shown that a newly synthesized polypeptide exhibited an identical electrophoretic mobility as the purified enzyme.

Animals↗

Chromogenic immunodetection of human serum albumin and alpha-L-fucosidase clones in a human hepatoma cDNA expression library.

A human hepatoma cDNA library was constructed in lambda gt11, a bacteriophage vector that was designed to express cDNA-encoded antigenic determinants in Escherichia coli. The cDNA expression library contained approximately 8 X 10(6) recombinant phages with an average insert size of 780 bp. The feasibility of using a chromogenic immunodetection procedure to isolate cDNA clones was proved by isolating a human serum albumin (HSA) cDNA clone. An approximately 1.0-kb cDNA clone was then isolated by screening the library with rabbit anti-human alpha-L-fucosidase antibodies. The identity of the alpha-L-fucosidase cDNA clone was confirmed by DNA sequence analysis and a comparison of the predicted amino acid sequence to the amino acid sequences of human alpha-L-fucosidase tryptic peptides.

Bacteriophage lambda↗

New map of bacteriophage lambda DNA.

A map of bacteriophage lambda was constructed, including accurate positions for all 41 cut sites made by 12 different restriction enzymes. Over 100 fragments from single, multiple, and partial enzyme digestions were measured versus standards that were calibrated with respect to DNA molecules of known sequence. The data were subjected to least-squares analysis to assign map coordinates. In no case did a fragment size predicted from the map differ from the measurement of the fragment by more than +/- 5%. This low error rate was consistent in all size ranges of fragments. The total length of lambda was calculated as 49,133 nucleotide pairs. This probably is accurate to within 500 base pairs.

Bacteriophage lambda↗

Restriction maps for twenty-one Charon vector phages.

The mapping of the sites of cleavage of nine restriction endonucleases (EcoRI, HindIII, BamHI, SalI, KpnI, SstI, BglII, XhoI, and XbaI) on 21 Charon phage vectors is described. Maps of individual subsections were obtained and then combined to assemble the complete vector maps. Calculations of maximum and minimum sizes of inserts which may be carried by the vectors using different restriction endonucleases or pairs of restriction endonucleases are presented. The regions mapped include several parts of phi 80 that had not been mapped previously.

Bacteriophage lambda↗