אסיף מאגר המחקר החקלאי

Histone methylation controls telomerase-independent telomere lengthening in cells undergoing dedifferentiation

Year:

2007

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Authors :

Volume :

306

Co-Authors:

Grafi, G., Albert Katz Department of Dryland Biotechnologies, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, 84990, Israel
Ben-Meir, H., Department of Plant Sciences, The Weizmann Institute of Science, Rehovot, 76100, Israel
Avivi, Y., Department of Plant Sciences, The Weizmann Institute of Science, Rehovot, 76100, Israel
Moshe, M., Albert Katz Department of Dryland Biotechnologies, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, 84990, Israel
Dahan, Y., Institute of Plant Sciences, ARO, The Volcani Center, Bet-Dagan, 50250, Israel
Zemach, A., Department of Plant Sciences, The Weizmann Institute of Science, Rehovot, 76100, Israel

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Abstract:

Cellular dedifferentiation underlies topical issues in biology such as regeneration and nuclear cloning and has common features in plants and animals. In plants, this process characterizes the transition of differentiated leaf cells to protoplasts (plant cells devoid of cell walls) and is accompanied by global chromatin reorganization associated with reprogramming of gene expression. A screen for mutants defective in proliferation and callus formation identified kyp-2-a mutant in the KRYPTONITE (KYP)/SUVH4 gene encoding a histone H3 lysine 9 (H3K9) methyltransferase. Analysis of telomere length revealed stochastic telomerase-independent lengthening of telomeres in wild type but not in kyp-2 protoplasts. In kyp-2 mutant, telomeric repeats were no longer associated with dimethylated H3K9. The Arabidopsis telomerase reverse transcriptase (tert) mutant displayed accelerated proliferation despite its short telomeres, though it also showed accelerated cell death. Microarray analysis uncovered several components of the ubiquitin proteolytic system, which are downregulated in kyp-2 compared to wild-type protoplasts. Thus, our results suggest that histone methylation activity is required for the establishment/maintenance of the dedifferentiated state and/or reentry into the cell cycle, at least partly, through activation of genes whose products are involved in the ubiquitin proteolytic pathway. In addition, our results illuminate the complexity of cellular dedifferentiation, particularly the occurrence of DNA recombination that can lead to genome instability. © 2007 Elsevier Inc. All rights reserved.

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