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H J Lipps

Publications and source records attributed to H J Lipps.

At least 37 records · Page 2Linked to original sources
PubMed1995

The processing of macronuclear-destined DNA sequences microinjected into the macronuclear anlagen of the hypotrichous ciliate Stylonchia lemnae.

We describe the construction of a vector carrying the micronuclear versions of two macronuclear DNA molecules, one of which was modified by the insertion of a polylinker sequence. This vector was injected into the polytene chromosomes of the developing macronucleus of Stylonychia and its processing during further macronuclear development and its fate in the mature macronucleus were analyzed. In up to 30% of injected cells the modified macronuclear DNA sequence could be detected. While the internal eliminated sequences (IES) present in the macronuclear precursor DNA sequence are still retained in the mature macronucleus, the modified macronuclear DNA sequence is correctly cut out from the vector, telomeres are added de novo and it is stably retained in the macronucleus during vegetative growth of the cells. This vector system represents an experimental system that allows the identification of DNA sequences involved in the processing of macronuclear DNA sequences during macronuclear development.

Animals↗
PubMed1993

Inhibition of HIV-1 replication by a high-copy-number vector expressing antisense RNA for reverse transcriptase.

We report the construction of a high-copy-number (hcn) expression vector for human cells. Amplification of this vector occurs due to the presence of an element derived from the murine DNA encoding ribosomal RNA (rDNA). HIV-1 replication in Jurkat T lymphocytes is nearly abolished when antisense RNA directed against the gene encoding reverse transcriptase is expressed from this hcn vector. The replication of the virus is only slightly reduced by the plasmid control version lacking the murine amplification-promoting element. This kind of hcn vector may represent an important improvement for the genetic engineering of eukaryotic cells and may also provide some ideas for the future gene therapy of some human diseases.

Culture Media, Conditioned↗
PubMed1993

The organization of internal telomeric repeats in the polytene chromosomes of the hypotrichous ciliate Stylonychia lemnae.

There exist about 1000-1500 internal telomeric sequences per haploid genome in the polytene chromosomes of the hypotrichous ciliate Stylonychia lemnae. All these telomeric repeats are contained in a very conserved element. This element consists of two 2 kb direct repeats flanking a 2.6 kb sequence. Immediately adjacent to one of the repeats a 18mer C4A4C4A4C2 telomeric sequence is localized. Sequences homologous to macronuclear DNA follow 180 bp downstream of the C4A4-bloc. These macronuclear homologous sequences are flanked by the second direct repeat. The possible origin and function of these telomere containing elements is discussed.

Animals↗
PubMed1993

Analysis of the subtelomeric regions of macronuclear gene-sized DNA molecules of the hypotrichous ciliate Stylonychia lemnae: implications for the DNA fragmentation process during macronuclear development?

The subtelomeric regions of macronuclear gene-sized DNA molecules from Stylonychia lemnae were analyzed. The results obtained indicate that these regions show a highly ordered and common sequence organization: Immediately adjacent to the telomeric sequence a short inverted repeat sequence is found, followed by another 7-9 bp inverted repeat sequence at approximately position 40. A 10 bp consensus sequence found in the subtelomeric regions of all gene-sized DNA molecules is found at approximately position 60 and in addition at about the same position palindromic sequences showing no homology to each other are localized. The biological significance of this sequence organization is discussed.

Animals↗
PubMed1993

The processing of macronuclear DNA sequences during macronuclear development of the hypotrichous ciliate Stylonychia lemnae.

The organization of two macronuclear DNA sequences in the polytene chromosomes of the hypotrichous ciliate Stylonychia lemnae and their processing from the micronucleus via the polytene chromosome stage up to the macronucleus was analyzed. The overall organization of these sequences in the polytene chromosomes resembles that described for the micronucleus of other hypotrichous ciliates, i.e. they are interrupted by internal eliminated sequences and not associated with telomeric sequences. The spacer region between the genes is bordered by direct repeats and inverted repeats are found at the termini of macronuclear sequences and in the spacer region. The organization of these macronuclear DNA sequences in the micronucleus was analyzed by polymerase chain reactions. The results obtained show that in the sequences analyzed no DNA reorganization occurs during polytene chromosome formation.

Animals↗
PubMed1991

Native yeast telomeres are sufficient to stabilize linear DNA in Xenopus laevis oocytes.

We have constructed a linear plasmid in yeast containing the entire bovine papillomavirus genome and tested its physical stability following microinjection into stage VI oocytes of Xenopus laevis. Our results show that unmodified telomeres, in contrast to the yeast-passaged telomeres, drastically affect the stability of the injected linear plasmid. Plasmids carrying unmodified Tetrahymena thermophila telomeric sequences are rapidly degraded in oocytes. When these plasmids are passed through yeast, the telomere ends become modified by the addition of yeast telomeric sequences. These plasmids are stably maintained in X. laevis oocytes, demonstrating that yeast-modified telomeres are sufficient to prevent linear DNA degradation.

Animals↗
PubMed1990

The two macronuclear histone H4 genes of the hypotrichous ciliate Stylonychia lemnae.

Macronuclear DNA of hypotrichous ciliates is organized in short gene-sized molecules, each containing all regulatory sequences for autonomous replication and expression. In these organisms the histone genes are not clustered but dispersed on different molecules of various sizes. Two histone H4 genes containing fragments, one of 1.7 kb and one of 2.8 kb, were found in the macronucleus of Stylonychia lemnae. Restriction and sequence data reveal that the two genes-sized pieces are derived from different micronuclear precursors. Both histone H4 genes code for the same protein of 103 aminoacids but differ greatly in their 5'-and 3'-regions.

Amino Acid Sequence↗
PubMed1986

A linear shuttle vector for yeast and the hypotrichous ciliate Stylonychia.

A linear plasmid was constructed in vitro using the telomeres of the rDNA of Tetrahymena pyriformis. These telomeres were added to a yeast circular vector containing an ARS sequence from Dictyostelium, the LEU2 gene of yeast and the neo gene from Escherichia coli Tn5 fused with a eukaryotic promoter. The resulting plasmid was used to transform yeast. During the replication of the linear plasmid in yeast it was spontaneously modified at the extremity by the addition of 300 bp of yeast telomeric sequence for each end. Total DNA prepared from yeast transformants was used to transform the hypotrichous ciliate Stylonychia lemnae. The same plasmid isolated from Stylonychia can again be replicated in yeast.

Animals↗
PubMed1984

Isolation and functional property of mRNAs coding for human interleukin 2.

Interleukin 2 (IL 2) is a lymphokine with specific growth promoting properties for activated T cells. The isolation and purification of specific mRNAs coding for this protein is reported. The analysis of total poly A + containing RNA from PHA stimulated T lymphocytes on agarose gels reveals the existence of at least two different IL-2 mRNAs. Isolated RNAs have been microinjected separately into Xenopus laevis oocytes for translation and consecutively the synthesized proteins were tested for activity on alloactivated T cell lines which were dependent on IL-2 for growth. Both RNAs coded for a protein which displayed clearly detectable IL-2 activity.

Animals↗
PubMed1983

A transformation system for the hypotrichous ciliate Stylonychia mytilus.

We describe a transformation system for the ciliate Stylonychia mytilus. The neomycin resistance gene from Escherichia coli transposon Tn5, which codes for the enzyme phosphotransferase and confers resistance to the antibiotic G 418, was ligated into macronuclear ;gene-size' DNA molecules. Using this recombinant DNA for transformation experiments we show that the gene is replicated and expressed in transformed cells.

Journal Article↗
PubMed1983

Antibodies against Z DNA react with the macronucleus but not the micronucleus of the hypotrichous ciliate stylonychia mytilus.

Using indirect immunofluorescence, we studied the reaction of antibodies specific for left-handed Z DNA with the nuclei of the hypotrichous ciliate Stylonychia mytilus. In the vegetative cell, the macronucleus reacts strongly with these antibodies, but no reaction can be detected with micronuclei. However, an antibody that binds to denatured and right-handed B DNA reacts with both types of nuclei. No reaction of the anti-Z DNA antibody is seen in the macronuclear replication band. Digestion of macronuclei with DNAase I leads to a decrease in the anti-Z DNA antibody reaction. Some stages of the developing macronucleus were also investigated. No reaction is seen at the polytene chromosome stage, but following DNA elimination the nucleus is seen to react with the antibody.

Animals↗
PubMed1982

Higher order DNA structure in macronuclear chromatin of the hypotrichous ciliate Oxytricha nova.

On lysis of macronuclei from the ciliated protozoan Oxytricha at 0.5-2 M NaCl, the DNA, which is normally found as discrete molecules ranging from 0.5 to 20 kilobases, appears in high molecular weight aggregates. Various treatments of the macronuclear lysate (i.e., nucleases, proteases, variation of salt, pH, and temperature) indicate that preservation of the aggregate structure depends on both nucleic acid-nucleic acid and nucleic acid-protein interactions. Purification of the DNA-protein complex after lysing the nuclei in 2 M NaCl shows that one major nuclear protein copurifies with the DNA. As shown by DNA-protein binding experiments, this protein has a high affinity for DNA; however, no evidence for sequence specificity of the protein binding was obtained. Chromatin reconstitution experiments suggest that the protein in itself is not sufficient for DNA aggregation in nuclei, but other factors, possibly the native chromatin structure, are required. Electron microscopy of the purified DNA-protein complex showed structures similar to those observed previously with in vitro-aggregated purified macronuclear DNA (14). A model is presented in which the terminal inverted repeat sequences found on all macronuclear DNA molecules interact with each other forming multistranded DNA complexes. The formation of these structures may be accelerated and stabilized by a protein in vivo.

Animals↗