The Arabidopsis thaliana homolog of yeast BRE1 has a function in cell cycle regulation during early leaf and root growth.
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.
Fleury
Delphine
D
Department of Plant Systems Biology, Flanders Institute for Biotechnology, Ghent University, B-9052 Gent, Belgium.
Himanen
Kristiina
K
Cnops
Gerda
G
Nelissen
Hilde
H
Boccardi
Tommaso Matteo
TM
Maere
Steven
S
Beemster
Gerrit T S
GT
Neyt
Pia
P
Anami
Sylvester
S
Robles
Pedro
P
Micol
José Luis
JL
Inzé
Dirk
D
Van Lijsebettens
Mieke
M
D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002453:Cell Cycle / Q000502:physiology*; D049109:Cell Proliferation; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D006801:Humans; D008025:Ligases / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D020411:Oligonucleotide Array Sequence Analysis; D010641:Phenotype; D018515:Plant Leaves / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism; D018517:Plant Roots / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D025801:Ubiquitin / Q000378:metabolism; D043743:Ubiquitin-Protein Ligase Complexes / Q000235:genetics / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*
D029681:Arabidopsis Proteins; C472168:Bre1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D025801:Ubiquitin; D043743:Ubiquitin-Protein Ligase Complexes; C521255:HUB1 protein, Arabidopsis; D044767:Ubiquitin-Protein Ligases; D008025:Ligases; C452202:HUB1 protein, S cerevisiae