Identification of Arabidopsis SUMO-interacting proteins that regulate chromatin activity and developmental transitions

Proc Natl Acad Sci U S A. 2013 Dec 3;110(49):19956-61. doi: 10.1073/pnas.1319985110. Epub 2013 Nov 19.

Abstract

Posttranslational modification of proteins by small ubiquitin-like modifier (SUMO) plays essential roles in eukaryotic growth and development. Many covalently modified SUMO targets have been identified; however, the extent and significance of noncovalent interactions of SUMO with cellular proteins is poorly understood. Here, large-scale yeast two-hybrid screens repeatedly identified a surprisingly small number of proteins that interacted with three Arabidopsis SUMO isoforms. These SUMO-interacting proteins are nuclear and fall into two main categories: six histone or DNA methyltransferses or demethylases and six proteins that we show to be the evolutionary and functional homologs of SUMO-targeted ubiquitin ligases (STUbLs). The selectivity of the screen for several methylases and demethylases suggests that SUMO interaction with these proteins has a significant impact on chromatin methylation. Furthermore, the Arabidopsis STUbLs (AT-STUbLs) complemented to varying degrees the growth defects of the Schizosaccharomyces pombe STUbL mutant rfp1/rfp2, and three of them also complemented the genome integrity defects of this mutant, demonstrating that these proteins show STUbL activity. We show that one of the AT-STUbLs least related to the S. pombe protein, AT-STUbL4, has acquired a plant-specific function in the floral transition. It reduces protein levels of CYCLING DOF FACTOR 2, hence increasing transcript levels of CONSTANS and promoting flowering through the photoperiodic pathway.

Keywords: CDF; Flowering time; Nucleolus; SIM; Slx5/Slx8.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / genetics*
  • Arabidopsis / growth & development*
  • Arabidopsis / metabolism
  • Arabidopsis Proteins / metabolism*
  • Chromatin / metabolism
  • DNA Primers / genetics
  • Gene Library
  • Methylation
  • Nuclear Proteins / metabolism
  • Two-Hybrid System Techniques
  • Ubiquitins / metabolism*

Substances

  • Arabidopsis Proteins
  • Chromatin
  • DNA Primers
  • Nuclear Proteins
  • SUMO protein, plant
  • Ubiquitins