Abstract
The survival of an organism’s progeny depends on the maintenance of its genome. Programmed DNA rearrangement and repair in Tetrahymena occur during the differentiation of the developing somatic macronuclear genome from the germ line micronuclear genome. Tetrahymena chromodomain protein (Tcd1) exhibited dynamic localization from the parental to the developing macronuclei. In the developing macronuclei, Tcd1 colocalized with Pdd1 and H3K9me3. Furthermore, Tcd1 colocalized with Pdd1 in the conjusome and “donut structure” of DNA elimination heterochromatin region. During the growth and conjugation stages, TCD1 knockout cells appeared normal and similar to wild-type strains. In addition, these knockout cells proceeded to the 2MAC-1MIC stage. However, the progeny of the TCD1 knockout cells did not grow upon return to SPP medium and eventually died. The deletion of the internal elimination sequence R element was partially disrupted in the developing new macronuclei. Gamma H2A staining showed that Tcd1 loss induced the accumulation of DNA double-strand breaks and the failure of genome repair. These results suggest that the chromodomain protein Tcd1 is required for the rearrangement and repair of new macronuclear genome in Tetrahymena.
Highlights
The survival of an organism’s progeny depends on the maintenance of its genome
Gamma H2A staining showed that Tcd[1] loss induced the accumulation of DNA double-strand breaks and the failure of genome repair. These results suggest that the chromodomain protein Tcd[1] is required for the rearrangement and repair of new macronuclear genome in Tetrahymena
The first genome rearrangement is the deletion of internal eliminated sequences (IESs), which is accompanied by the ligation of the flanking macronucleus-destined sequences[5]
Summary
The survival of an organism’s progeny depends on the maintenance of its genome. Programmed DNA rearrangement and repair in Tetrahymena occur during the differentiation of the developing somatic macronuclear genome from the germ line micronuclear genome. Gamma H2A staining showed that Tcd[1] loss induced the accumulation of DNA double-strand breaks and the failure of genome repair These results suggest that the chromodomain protein Tcd[1] is required for the rearrangement and repair of new macronuclear genome in Tetrahymena. The deletion of the internal elimination sequence R element was disrupted in the newly developing new macronuclei and γ -H2A.X foci were maintained throughout the late conjugation stage in TCD1 knockout strains. These results suggest that Tcd[1] plays roles in genome rearrangement and repair in Tetrahymena
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