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

Idan Pereman, Assaf Mosquna, Aviva Katz, Gertrud Wiedemann, Daniel Lang, Eva L. Decker, Yosuke Tamada, Takaaki Ishikawa, Tomoaki Nishiyama, Mitsuyasu Hasebe, Ralf Reski*, Nir Ohad

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


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.

Original languageEnglish
Pages (from-to)860-870
Number of pages11
JournalBiochimica et Biophysica Acta - Gene Regulatory Mechanisms
Issue number7
StatePublished - 1 Jul 2016


FundersFunder number
German Federal and States Governments
German Israeli Foundation154/2008
Manna foundation
Japan Society for the Promotion of Science16H06378
Ministry of Education, Culture, Sports, Science and Technology


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


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