Arabidopsis thaliana Homolog of Yeast BRE1 Has a Function in Cell Cycle Regulation during Early Leaf and Root Growth

• Published in: The Plant cell 2007-02, Vol.19 (2), p.417-432
• Main Authors: Fleury, Delphine, Himanen, Kristiina, Cnops, Gerda, Nelissen, Hilde, Boccardi, Tommaso Matteo, Maere, Steven, Beemster, Gerrit T.S, Neyt, Pia, Anami, Sylvester, Robles, Pedro, Micol, José Luis, Inzé, Dirk, Van Lijsebettens, Mieke
• Format: Article
• Language: English
• Subjects: Arabidopsis - genetics; Arabidopsis - metabolism; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Arabidopsis thaliana; Cell cycle; Cell Cycle - physiology; Cell cycle proteins; Cell growth; Cell Proliferation; Epidermal cells; Gene Expression Profiling; Gene Expression Regulation, Plant; Genes; Humans; Ligases - genetics; Ligases - metabolism; Molecular Sequence Data; Oligonucleotide Array Sequence Analysis; Phenotype; Plant cells; Plant growth; Plant growth regulators; Plant Leaves - cytology; Plant Leaves - growth & development; Plant Leaves - metabolism; Plant Roots - cytology; Plant Roots - growth & development; Plant Roots - metabolism; Plants; Proteins; Saccharomyces cerevisiae Proteins - genetics; Saccharomyces cerevisiae Proteins - metabolism; Transcriptional Activation; Transcriptional regulatory elements; Ubiquitin - metabolism; Ubiquitin-Protein Ligase Complexes - genetics; Ubiquitin-Protein Ligase Complexes - metabolism; Ubiquitin-Protein Ligases - genetics; Ubiquitin-Protein Ligases - metabolism; Yeasts
• ISSN: 1040-4651; 1532-298X; 1532-298X
• DOI: 10.1105/tpc.106.041319

Chromatin modification and transcriptional activation are novel roles for E3 ubiquitin ligase proteins that have been mainly associated with ubiquitin-dependent proteolysis. We identified HISTONE MONOUBIQUITINATION1 (HUB1) (and its homolog HUB2) in Arabidopsis thaliana as RING E3 ligase proteins with a function in organ growth. We show that HUB1 is a functional homolog of the human and yeast BRE1 proteins because it monoubiquitinated histone H2B in an in vitro assay. Hub knockdown mutants had pale leaf coloration, modified leaf shape, reduced rosette biomass, and inhibited primary root growth. One of the alleles had been designated previously as ang4-1. Kinematic analysis of leaf and root growth together with flow cytometry revealed defects in cell cycle activities. The hub1-1 (ang4-1) mutation increased cell cycle duration in young leaves and caused an early entry into the endocycles. Transcript profiling of shoot apical tissues of hub1-1 (ang4-1) indicated that key regulators of the G2-to-M transition were misexpressed. Based on the mutant characterization, we postulate that HUB1 mediates gene activation and cell cycle regulation probably through chromatin modifications.