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Biomedical subjects

M R Lauth

Publications and source records attributed to M R Lauth.

7 recordsLinked to original sources
PubMed1987

The Yarrowia lipolytica LEU2 gene.

A 2810 bp DNA fragment containing the beta-isopropylmalate dehydrogenase gene of the dimorphic yeast Yarrowia lipolytica has been sequenced. The sequence contains an open reading frame of 405 codons, predicting a protein of 43,366 molecular weight. Protein sequence homology with the polypeptide encoded by the LEU2 gene of Saccharomyces cerevisiae is 64%, whereas DNA sequence homology is 61%. The 5'- and 3'-flanking regions of the Y. lipolytica LEU2 gene share only some general structural features common to genes of S. cerevisiae such as the presence and location of TATA boxes, CAAT boxes, CACACA repeats, the lack of G residues in the 5'-untranslated region and 3'-transcription terminators. Transcription of a 1.4 kb mRNA begins at a small cluster of sites approximately 40 base pairs before the initial ATG.

3-Isopropylmalate Dehydrogenase↗
PubMed1982

Transposon-mediated site-specific recombination: identification of three binding sites for resolvase at the res sites of gamma delta and Tn3.

The tnpR gene product, resolvase, of the transposable element gamma delta mediates site-specific recombination between two copies of gamma delta directly repeated on the same replicon, and it negatively regulates transcription of the tnpA (transposase) gene and its own gene. The recombinational site, res, and the regulatory region both are located in the tnpA-tnpR intercistronic region. In studying the interaction of purified resolvase with DNA fragments derived from gamma delta and the related transposon, Tn3, that span this region, we have demonstrated that three sites specifically bind resolvase. Site I overlaps the recombinational crossover point and both transcriptional promoters. Sites II and III cover most of the DNA between the crossover point and the translational start of the tnpR gene. These are the only binding sites we have detected in a region of about 400 base pairs centered on the crossover point. Studies of cointegrates that contain only part of the region that binds resolvase indicate that site I is not sufficient for efficient site-specific recombination and suggest that all three sites are probably required.

Binding Sites↗
PubMed1976

Polytene chromosomes of Oxytricha: biochemical and morphological changes during macronuclear development in a ciliated protozoan.

After conjugation in the ciliated protozoan, Oxytricha, polytene chromosomes are formed during the development of a macronucleus from a micronucleus. Here we report a microscopic study of these chromosomes and an analysis of their DNA. The polytene chromosomes of Oxytricha bear a strong morphological resemblance to the polytene chromosomes of the Dipteran salivary gland. The nucleus of a developing macronuclear anlage contains 120 +/- 2 polytene chromosomes and each chromosome has an average of 81 hands; a total of about 10,000 bands per nucleus. At a later stage in development, the number of bands per chromosome is reduced by a factor of four, presumably due to fusion of adjacent bands. The polytene chromosomes then break up into their constituent bands, each of which is encased in a vesicle. There are about 2,700 vesicles per nucleus.--During the growth of polytene chromosomes, there is a change in the relative proportion of sequences in the DNA. The DNA from polytene nuclei has a buoyant density of 1.695 g/cc, significantly lighter than the density of the original micronuclear DNA (1.698 G/cc to 1.702 g/cc). We interpret this buoyant density change to be the result of differential replication of DNA sequences during polytene chromosome growth. A second change in DNA composition occurs after the polytene stage of development, shown by a shift in buoyant density to 1.701 g/cc in the DNA of the mature macronucleus. During this second process, the molecular weight of the DNA is reduced from greater than 50 x 10(6) daltons to about 2 x 10(6) daltons.

Animals↗
PubMed1976

DNA of ciliated protozoa: DNA sequence diminution during macronuclear development of Oxytricha.

We have measured the reassociation kinetics of DNA from the micronucleus and from the macronucleus of the hypotrichous ciliate Oxytricha. The micronuclear DNA reassociates with at least a two-component reaction, indicating the presence of both repeated and non-repeated sequences. The kinetic complexity of micronuclear non-repeated DNA is in the range of 2 to 15 X 10(11) daltons; the haploid DNA content of the micronucleus is 4 X 10(11) daltons (0.66 pg), measured microspectrophotometrically. The DNA of the macronucleus reassociates as a single second-order reaction, with a kinetic complexity of 3.6 X 10(10) daltons. A comparison of the kinetic complexities of micronuclear and macronuclear DNAs suggest a 5 to 30 fold reduction in DNA sequence complexity during the formation of a macronucleus from a micronucleus. Macronuclear DNA is in pieces with an average molecular weight of 2.1 X 10(6) daltons. Since the kinetic complexity of macronuclear DNA is 3.6 X 10(10) daltons, the macronucleus must contain about 17,000 different kinds of DNA pieces. Each macronucleus contains 3.5 X 10(13) daltons (58 pg) of DNA, indicating that each sequence must be present about 1000 times per macronucleus or 2000 times per cell.

Animals↗