Tomas Simonsson

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Telomere end-binding proteins (TEBPs) bind to the guanine-rich overhang (G-overhang) of telomeres. Although the DNA binding properties of TEBPs have been investigated in vitro, little is known about their functions in vivo. Here we use RNA interference to explore in vivo functions of two ciliate TEBPs, TEBPalpha and TEBPbeta. Silencing the expression of(More)
Nucleic acid structure-function correlations are pivotal to major biological events like transcription, replication, and recombination. Depending on intracellular conditions in vivo and buffer composition in vitro, DNA appears capable of inexhaustible structure variation. At moderately acidic, or even neutral pH, DNA strands that are rich in cytosine bases(More)
Positioned nucleosomes are believed to play important roles in transcriptional regulation and for the organization of chromatin in cell nuclei. Here, we have isolated the DNA segments in the mouse genome that form the most stable nucleosomes yet characterized. In separate molecules we find phased runs of three to four adenine nucleotides, extensive CA(More)
To be functional, nucleic acids need to adopt particular three-dimensional structures. For a long time DNA was regarded as a rigid and passive molecule with the sole purpose to store genetic information, but experimental data has now accumulated that indicates the full dynamic repertoire of this macromolecule. During the last decade, four-stranded DNA(More)
The c-myc oncogene is one of the most commonly malfunctioning genes in human cancers, and is an attractive target for anti-gene therapy. Although synthetic oligonucleotides designed to silence c-myc expression via one of its major control elements function well in vitro, their mode of action has been indefinite. Here we show that the targeted control(More)
The telomeric G-overhangs of the ciliate Stylonychia lemnae fold into a G-quadruplex DNA structure in vivo. Telomeric G-quadruplex formation requires the presence of two telomere end binding proteins, TEBPalpha and TEBPbeta, and is regulated in a cell-cycle dependent manner. Unfolding of this structure in S phase is dependent on the phosphorylation of(More)
Telomeres are protein-DNA complexes that cap chromosome ends and protect them from being recognized and processed as DNA breaks. Loss of capping function results in genetic instability and loss of cellular viability. The emerging view is that maintenance of an appropriate telomere structure is essential for function. Structural information on telomeric(More)
Nucleosomes, the building blocks of chromatin, are responsible for DNA packaging in eukaryotic cell nuclei. They play a structural role in genome condensation, and influence transcription and replication. Properties of the DNA sequence, such as curvature and flexibility, direct the location of nucleosomes. DNA sequences that position nucleosomes have been(More)
Whereas mammalian cells harbor two double strand telomeric repeat binding factors, TRF1 and TRF2, the fission yeast Schizosaccharomyces pombe has been thought to harbor solely the TRF1/TRF2 ortholog Taz1p to perform comparable functions. Here we report the identification of telomeric repeat binding factor 1 (Tbf1), a second TRF1/TRF2 ortholog in S. pombe.(More)
Somatic cell nuclear transfers and the generation of induced pluripotent stem cells provide potential routes towards non-immunogenic cell replacement therapies. Translationally controlled tumor protein (Tpt1) was recently suggested to regulate cellular pluripotency. Here we explore functions of Tpt1 in mouse embryonic stem (ES) cells. We find that Tpt1 is(More)