title: Mitotic lifecycle of chromosomal 3xHMG-box proteins and the role of their N-terminal domain in the association with rDNA loci and proteolysis.
abstract: The high mobility group (HMG)-box is a DNA-binding domain characteristic of various eukaryotic DNA-binding proteins. 3xHMG-box proteins (containing three copies of the HMG-box domain and a unique basic N-terminal domain) are specific for plants and the Arabidopsis genome encodes two versions termed 3xHMG-box1 and 3xHMG-box2, whose expression is cell cycle-dependent, peaking during mitosis. Here, we analysed in detail the spatiotemporal expression, subcellular localisation and chromosome association of the Arabidopsis thaliana 3xHMG-box proteins. Live cell imaging and structured illumination microscopy revealed that the expression of the 3xHMG-box proteins is induced in late G2 phase of the cell cycle and upon nuclear envelope breakdown in prophase they rapidly associate with the chromosomes. 3xHMG-box1 associates preferentially with 45S rDNA loci and the basic N-terminal domain is involved in the targeting of rDNA loci. Shortly after mitosis the 3xHMG-box proteins are degraded and an N-terminal destruction-box mediates the proteolysis. Ectopic expression/localisation of 3xHMG-box1 in interphase nuclei results in reduced plant growth and various developmental defects including early bolting and abnormal flower morphology. The remarkable conservation of 3xHMG-box proteins within the plant kingdom, their characteristic expression during mitosis, and their striking association with chromosomes, suggest that they play a role in the organisation of plant mitotic chromosomes.
authors.affiliation: Cell Biology and Plant Biochemistry, Biochemie-Zentrum Regensburg, University of Regensburg, Universitätsstr. 31, D-93053, Regensburg, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Antosch
authors.affiliation: Leibniz Institute of Plant Genetics and Crop Plant Research (IPK) Gatersleben, Corrensstr. 3, D-06466, Stadt Seeland, Germany.
authors.forename: Veit
authors.initials: V
authors.lastname: Schubert
authors.affiliation: Cell Biology and Plant Biochemistry, Biochemie-Zentrum Regensburg, University of Regensburg, Universitätsstr. 31, D-93053, Regensburg, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Holzinger
authors.affiliation: Leibniz Institute of Plant Genetics and Crop Plant Research (IPK) Gatersleben, Corrensstr. 3, D-06466, Stadt Seeland, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Houben
authors.affiliation: Cell Biology and Plant Biochemistry, Biochemie-Zentrum Regensburg, University of Regensburg, Universitätsstr. 31, D-93053, Regensburg, Germany.
authors.forename: Klaus D
authors.initials: KD
authors.lastname: Grasser
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D002467:Cell Nucleus; D032461:Chromosomes, Plant; D018744:DNA, Plant; D004275:DNA, Ribosomal; D018506:Gene Expression Regulation, Plant; D056426:Genetic Loci; D024742:HMG-Box Domains; D024002:HMGB Proteins / Q000378:metabolism*; D008938:Mitosis; D059748:Proteolysis
chemical_list: D029681:Arabidopsis Proteins; D018744:DNA, Plant; D004275:DNA, Ribosomal; D024002:HMGB Proteins
keywords: Arabidopsis; HMGB; chromatin; high mobility group (HMG)-box domain; mitotic chromosome; rDNA; selective proteolysis