1. Programmed DNA-reorganization in ciliates, 2. The regulation of telomere structure, 3. The epigenetic regulation of replication

in Witten

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Programmed DNA-reorganization in ciliates
Programmed DNA-reorganization and elimination processes are frequently found during cellular differentiation in eukaryotes but never to the same extend as observed in ciliated protozoa. These unicellular organisms contain two types of nuclei within one cell, the large macronucleus and the diploid micronucleus. While the macronucleus is transcriptionally active and provides all information for vegetative growth, the heterochromatic micronucleus is transcriptionally inert. Only after sexual reproduction a new macronucleus is formed from a micronuclear derivative. In the course of macronuclear differentiation dramatic DNA-reorganization and elimination processes occur. These include splicing of internal DNA sequences, elimination of a large percentage of micronuclear specific sequences, fragmentation of the macronuclear genome into small “nanochromosomes”, de novo addition of telomeres to these nanochromosomes and amplification to a specific copy number. In addition, very often macronuclear destined sequences occur in a scrambled disorder and have to be reordered to result in a functional gene. We study cis-acting sequences as well as trans-acting factors involved in this nuclear differentiation process and will determine the biological function of genes exclusively expressed during macronuclear development.

The regulation of telomere structure
Telomeres are specialized DNA-protein complexes at the ends of eukaryotic chromosomes. They are required for maintaining genome integrity and for correct replication of chromosomal ends. Telomeric sequences consist of short repeated sequences and the 3’ G-rich strand always forms a single stranded overhang. In vitro telomeric DNA sequences can adopt a variety of alternative DNA structures from which only the t-loop structure and G-quadruplex structure are stable under physiological conditions.

An extra-chromosomal mammalian replicon with focus on the epigenetic regulation of replication leading to advantageous gene therapy
In order to study the epigenetic regulation of replication a non-viral episomal vector system, pEPI, was constructed in our lab. Its functional elements are a transcription unit linked to a S/MAR sequence. An active transcription upstream of the S/MAR running into this sequence is required and even sufficient for episomal replication. This construct replicates episomally in mammalian cells and is mitotically stable in the absence of selection.


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Univ.-Prof. Dr. Hans Joachim Lipps
Raum: 1.042 Private Universität Witten/Herdecke gGmbH Stockumer Straße 10 58453 Witten, Germany

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