Death harmony played by nucleus and mitochondria: nuclear apoptosis during conjugation of tetrahymena.
Tetrahymena programmed nuclear death or nuclear apoptosis is a unique process during conjugation in which only the parental macronucleus is eliminated from the progeny cytoplasm, and other nuclei such as new micro- and macronuclei are unaffected. The nuclear death process consists of three successive steps: chromatin cleavage into high-molecular mass DNA, oligonucleosomal laddering concomitant with nuclear condensation, and complete degradation of the nuclear DNA. Following the first step of the death process, the parental macronucleus is engulfed by a large autophagosome in which many mitochondria are incorporated. Those sequestered mitochondria simply break down and release endonuclease similar to mammalian endonuclease G that is responsible for the generation of the DNA ladder, leading to the conclusion that mitochondria play a crucial role in the execution of the death program. Thus, the parental macronucleus is subject to final death by autophagy in collaboration with caspase-like enzymes, resulting in the ultimate outcome of nuclear resorption.
Endoh
Hiroshi
H
Division of Life Science, Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa, Japan.
Kobayashi
Takashi
T
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D001343:Autophagy / Q000502:physiology*; D002467:Cell Nucleus; D003227:Conjugation, Genetic / Q000502:physiology*; D004706:Endodeoxyribonucleases / Q000378:metabolism; D008928:Mitochondria / Q000502:physiology*; D010588:Phagosomes / Q000502:physiology*; D013768:Tetrahymena / Q000502:physiology*
D004706:Endodeoxyribonucleases; C052391:endonuclease G