tailieunhanh - Báo cáo khoa học: A possible role of mitochondria in the apoptotic-like programmed nuclear death of Tetrahymena thermophila Takashi Kobayashi and Hiroshi Endoh

The ciliated protozoanTetrahymenahas a unique apoptosis-like process, which is called programmed nuclear death (PND). During conjugation, the new germinal micro- and somatic macro-nuclei differentiate from a zygotic fertilized nucleus, whereas the old parental macronucleus degenerates, ensuring that only the new macronucleus is responsible for expression of the progeny genotype. | iFEBS Journal A possible role of mitochondria in the apoptotic-like programmed nuclear death of Tetrahymena thermophila Takashi Kobayashi and Hiroshi Endoh Division of Life Science Graduate Schoolof NaturalScience and Technology Kanazawa University Japan Keywords nuclear apoptosis autophagosome endonuclease mitochondria Tetrahymena Correspondence T. Kobayashi Institute for Molecular Science of Medicine Aichi Medical University Yazako Nagakute Aichi 480-1195 Japan Fax 81 561 63 3532 Tel 81 561 62 3311 ext. 2087 E-mail tacobys@ Received 13 April 2005 revised 19 July 2005 accepted 24 August 2005 doi The ciliated protozoan Tetrahymena has a unique apoptosis-like process which is called programmed nuclear death PND . During conjugation the new germinal micro- and somatic macro-nuclei differentiate from a zygotic fertilized nucleus whereas the old parental macronucleus degenerates ensuring that only the new macronucleus is responsible for expression of the progeny genotype. As is the case with apoptosis this process encompasses chromatin cleavage into high-molecular mass DNA oligonucleosomal DNA laddering and complete degradation of the nuclear DNA with the ultimate outcome of nuclear resorption. Caspase-8- and caspase-9-like activities are involved in the final resorption process of PND. In this report we show evidence for mitochondrial association with PND. Mitochondria and the degenerating macronucleus were colocalized in autophagosome using two dyes for the detection of mitochondria. In addition an endonuclease with similarities to mammalian endonuclease G was detected in the isolated mitochondria. When the macronuclei were incubated with isolated mitochondria in a cell-free system DNA fragments of 150-400 bp were generated but no DNA ladder appeared. Taking account of the present observations and the timing of autophagosome formation we conclude that mitochondria might be involved in Tetrahymena PND probably with the