SIZ1/SIZ2 control of chromosome transmission fidelity is mediated by the sumoylation of topoisomerase II.
The Smt3 (SUMO) protein is conjugated to substrate proteins through a cascade of E1, E2, and E3 enzymes. In budding yeast, the E3 step in sumoylation is largely controlled by Siz1p and Siz2p. Analysis of Siz- cells shows that SUMO E3 is required for minichromosome segregation and thus has a positive role in maintaining the fidelity of mitotic transmission of genetic information. Sumoylation of the carboxy-terminus of Top2p, a known SUMO target, is mediated by Siz1p and Siz2p both in vivo and in vitro. Sumoylation in vitro reveals that Top2p is an extremely potent substrate for Smt3p conjugation and that chromatin-bound Top2p can still be sumoylated, unlike many other SUMO substrates. By combining mutations in the TOP2 sumoylation sites and the SIZ1 and SIZ2 genes we demonstrate that the minichromosome segregation defect and dicentric minichromosome stabilization, both characteristic for Smt3p-E3-deficient cells, are mediated by the lack of Top2p sumoylation in these cells. A role for Smt3p-modification as a signal for Top2p targeting to pericentromeric regions was suggested by an analysis of Top2p-Smt3p fusion. We propose a model for the positive control of the centromeric pool of Top2p, required for high segregation fidelity, by Smt3p modification.
Takahashi
Yoshimitsu
Y
National Institutes of Health, National Institute of Child Health and Human Development, Laboratory of Gene Regulation and Development, Bethesda, Maryland 20892, USA.
Yong-Gonzalez
Vladimir
V
Kikuchi
Yoshiko
Y
Strunnikov
Alexander
A
D000595:Amino Acid Sequence; D002503:Centromere / Q000235:genetics / Q000378:metabolism; D043171:Chromosomal Instability / Q000235:genetics*; D015825:Chromosomes, Fungal / Q000201:enzymology / Q000235:genetics*; D015342:DNA Probes; D004250:DNA Topoisomerases, Type II / Q000378:metabolism*; D004843:Epistasis, Genetic; D008969:Molecular Sequence Data; D012097:Repressor Proteins / Q000502:physiology; D025842:SUMO-1 Protein / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000502:physiology*; D025841:Small Ubiquitin-Related Modifier Proteins; D044767:Ubiquitin-Protein Ligases / Q000502:physiology*
D015342:DNA Probes; D012097:Repressor Proteins; C099362:SMT3 protein, S cerevisiae; D025842:SUMO-1 Protein; D029701:Saccharomyces cerevisiae Proteins; C436836:Siz2 protein, S cerevisiae; D025841:Small Ubiquitin-Related Modifier Proteins; D044767:Ubiquitin-Protein Ligases; D004250:DNA Topoisomerases, Type II; C436837:Siz1 protein, S cerevisiae