Cooperation of sumoylated chromosomal proteins in rDNA maintenance.
SUMO is a posttranslational modifier that can modulate protein activities, interactions, and localizations. As the GFP-Smt3p fusion protein has a preference for subnucleolar localization, especially when deconjugation is impaired, the nucleolar role of SUMO can be the key to its biological functions. Using conditional triple SUMO E3 mutants, we show that defects in sumoylation impair rDNA maintenance, i.e., the rDNA segregation is defective and the rDNA copy number decreases in these mutants. Upon characterization of sumoylated proteins involved in rDNA maintenance, we established that Top1p and Top2p, which are sumoylated by Siz1p/Siz2p, most likely collaborate with substrates of Mms21p to maintain rDNA integrity. Cohesin and condensin subunits, which both play important roles in rDNA stability and structures, are potential substrates of Mms21, as their sumoylation depends on Mms21p, but not Siz1p and Siz2p. In addition, binding of cohesin and condensin to rDNA is altered in the mms21-CH E3-deficient mutant.
Laboratory of Gene Regulation and Development, National Institute of Child Health and Human Development, NIH, Bethesda, MD, USA.
Yoshimitsu
Y
Takahashi
Stanimir
S
Dulev
Xianpeng
X
Liu
Natalie Jasmin
NJ
Hiller
Xiaolan
X
Zhao
Alexander
A
Strunnikov
D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics / Q000378:metabolism*; D026942:DNA Topoisomerases / Q000235:genetics / Q000378:metabolism; D004271:DNA, Fungal / Q000235:genetics* / Q000378:metabolism*; D004275:DNA, Ribosomal / Q000235:genetics* / Q000378:metabolism*; D005800:Genes, Fungal; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D025842:SUMO-1 Protein / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D025841:Small Ubiquitin-Related Modifier Proteins / Q000235:genetics / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism
D002868:Chromosomal Proteins, Non-Histone; D004271:DNA, Fungal; D004275:DNA, Ribosomal; C500948:Mms21 protein, S cerevisiae; D009687:Nuclear Proteins; D025842:SUMO-1 Protein; D029701:Saccharomyces cerevisiae Proteins; C436836:Siz2 protein, S cerevisiae; D025841:Small Ubiquitin-Related Modifier Proteins; D044767:Ubiquitin-Protein Ligases; D026942:DNA Topoisomerases; C436837:Siz1 protein, S cerevisiae