| Autor: |
Akematsu T; Department of Chromosome Biology, University of Vienna, Vienna, Austria., Fukuda Y; Department of Biodiversity Science, Tohoku University, Oosaki, Japan.; Division of Biological Resource Science, Tohoku University, Oosaki, Japan.; Graduate School of Agricultural Science, Tohoku University, Oosaki, Japan., Garg J; Department of Biology, York University, Toronto, Canada., Fillingham JS; Department of Chemistry and Biology, Ryerson University, Toronto, Canada., Pearlman RE; Department of Biology, York University, Toronto, Canada., Loidl J; Department of Chromosome Biology, University of Vienna, Vienna, Austria. |
| Abstrakt: |
Based on observations of markers for DNA lesions, such as phosphorylated histone H2AX (γH2AX) and open DNA ends, it has been suggested that post-meiotic DNA double-strand breaks (PM-DSBs) enable chromatin remodeling during animal spermiogenesis. However, the existence of PM-DSBs is unconfirmed, and the mechanism responsible for their formation is unclear. Here, we report the first direct observation of programmed PM-DSBs via the electrophoretic separation of DSB-generated DNA fragments in the ciliate Tetrahymena thermophila . These PM-DSBs are accompanied by switching from a heterochromatic to euchromatic chromatin structure in the haploid pronucleus. Both a topoisomerase II paralog with exclusive pronuclear expression and Spo11 are prerequisites for PM-DSB induction. Reduced PM-DSB induction blocks euchromatin formation, characterized by histone H3K56 acetylation, leading to a failure in gametic nuclei production. We propose that PM-DSBs are responsible for histone replacement during the reprogramming of generative to undifferentiated progeny nuclei. |
