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Biochim Biophys Acta. 2016 Jul;1859(7):860-70. doi: 10.1016/j.bbagrm.2016.05.004. Epub 2016 May 11.

The Polycomb group protein CLF emerges as a specific tri-methylase of H3K27 regulating gene expression and development in Physcomitrella patens.

Author information

1
Department of Molecular Biology and Ecology of Plants, Tel-Aviv University, Tel-Aviv 69978, Israel.
2
Department of Molecular Biology and Ecology of Plants, Tel-Aviv University, Tel-Aviv 69978, Israel; Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, Faculty of Agriculture, Hebrew University of Jerusalem, Rehovot 7610001, Israel.
3
Plant Biotechnology, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany.
4
National Institute for Basic Biology, Okazaki 444-8585, Japan; Department of Basic Biology, The Graduate University for Advanced Studies, Okazaki 444-8585, Japan.
5
National Institute for Basic Biology, Okazaki 444-8585, Japan.
6
Advanced Science Research Center, Kanazawa University, Kanazawa 920-0934, Japan; ERATO, Okazaki 444-8585, Japan.
7
National Institute for Basic Biology, Okazaki 444-8585, Japan; Department of Basic Biology, The Graduate University for Advanced Studies, Okazaki 444-8585, Japan; ERATO, Okazaki 444-8585, Japan.
8
Plant Biotechnology, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany; FRIAS - Freiburg Institute for Advanced Studies, 79104 Freiburg, Germany; BIOSS - Centre for Biological Signaling Studies, 79104 Freiburg, Germany. Electronic address: ralf.reski@biologie.uni-freiburg.de.
9
Department of Molecular Biology and Ecology of Plants, Tel-Aviv University, Tel-Aviv 69978, Israel; FRIAS - Freiburg Institute for Advanced Studies, 79104 Freiburg, Germany; The Manna Center Program for Food Safety & Security, Tel Aviv University, 69978, Israel. Electronic address: niro@tauex.tau.ac.il.

Abstract

Packaging of eukaryotic DNA largely depends on histone modifications that affect the accessibility of DNA to transcriptional regulators, thus controlling gene expression. The Polycomb group (PcG) chromatin remodeling complex deposits a methyl group on lysine 27 of histone 3 leading to repressed gene expression. Plants encode homologs of the Enhancer of zeste (E(z)), a component of the PcG complex from Drosophila, one of which is a SET domain protein designated CURLY LEAF (CLF). Although this SET domain protein exhibits a strong correlation with the presence of the H3K27me3 mark in plants, the methyl-transferase activity and specificity of its SET domain have not been directly tested in-vivo. Using the evolutionary early-diverged land plant model species Physcomitrella patens we show that abolishment of a single copy gene PpCLF, as well as an additional member of the PcG complex, FERTILIZATION-INDEPENDENT ENDOSPERM (PpFIE), results in a specific loss of tri-methylation of H3K27. Using site-directed mutagenesis of key residues, we revealed that H3K27 tri-methylation is mediated by the SET domain of the CLF protein. Moreover, the abolishment of H3K27me3 led to enhanced expression of transcription factor genes. This in turn led to the development of fertilization-independent sporophyte-like structures, as observed in PpCLF and PpFIE null mutants. Overall, our results demonstrate the role of PpCLF as a SET protein in tri-methylation of H3K27 in-vivo and the importance of this modification in regulating the expression of transcription factor genes involved in developmental programs of P. patens.

KEYWORDS:

Curly leaf; Epigenetic regulation; H3K27 methylation; Histone code; Physcomitrella patens; SET domain

PMID:
27179444
DOI:
10.1016/j.bbagrm.2016.05.004
[Indexed for MEDLINE]

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