Distinctive properties of Arabidopsis SUMO paralogs support the in vivo predominant role of AtSUMO1/2 isoforms.

Laura Castaño-Miquel , Josep Seguí , L.Maria Lois (1)

1 Molecular Genetics

Protein modification by SUMO has emerged as an essential regulatory mechanism in eukaryotes. Even though the molecular mechanisms of SUMO conjugation/ deconjugation are conserved, the number of SUMO machinery components and their conservation degree are specific to each organism. Here, we present data contributing to the notion that the four expressed Arabidopsis SUMO paralogs, AtSUMO1, 2, 3 and 5, have functionally diverged to a higher extent than their human orthologs. We have explored the conservation degree of these paralogs and found that the surfaces involved in E1 activating enzyme recognition and E2 conjugating enzyme and SIM (SUMO Interacting Motif) non-covalent interactions are well conserved in AtSUMO1/2 isoforms, whereas AtSUMO3 shows a lower conservation degree and AtSUMO5 is the most divergent isoform. These differences are functionally relevant since AtSUMO3 and 5 are deficient in establishing E2 non-covalent interactions, which has not been reported for any naturally occurring SUMO ortholog. In addition, AtSUMO3 is less efficiently conjugated than AtSUMO1/2 and AtSUMO5 shows the lowest conjugation level. A mutagenesis analysis revealed that decreases in conjugation rate, and thioester bond formation, are the result of the non-conserved residues involved in E1 activating enzyme recognition that are present in AtSUMO3 and 5. Our results support a role for the E1 activating enzyme in SUMO paralog discrimination, providing a new mechanism to favor conjugation of the essential AtSUMO1/2 paralogs.

Mots clés: Life Sciences

Laura Castaño-Miquel, Josep Seguí, L.Maria Lois. Distinctive properties of Arabidopsis SUMO paralogs support the in vivo predominant role of AtSUMO1/2 isoforms.. Biochemical Journal, 2011, 436 (3), pp.581-590. ⟨10.1042/BJ20101446⟩. ⟨hal-00596266⟩