High impact information on SMT3

• The pattern of Smt3-coupled proteins in yeast changes markedly throughout the cell cycle, and specific conjugates accumulate in ulp1 mutants [1].
• Our results also suggest that at early meiotic prophase, Zip1 interacts with Zip3-independent Smt3 conjugates (e.g., Top2) to promote nonhomologous centromere coupling [2].
• Experiments with conditional uba2 mutants showed that Uba2p is required for Smt3p conjugation in vivo [3].
• Moreover, recombinant yeast and mammalian UBC9 enzymes were found to form thioester complexes with SMT3 and SUMO-1, respectively [4].
• The ubiquitin-like protein SMT3 from Saccharomyces cerevisiae and SUMO-1, its mammalian homolog, can be covalently attached to other proteins posttranslationally [4].

Biological context of SMT3

• A human HSMT3 cDNA encoding a homolog of the yeast SMT3, a suppressor of MIF2 mutations in a centromere protein gene, was identified and sequenced [5].
• Furthermore, UBA2 and AOS1 are both essential genes, providing additional evidence that they act in a distinct pathway whose role in cell viability is to conjugate Smt3p to other proteins [3].
• The absence of Ubc9 or Smt3 also resulted in defects in chromosome segregation [6].
• We also report an initial characterization of phenotypes associated with the SMT3/SUMO gene and the isolation of WSS1, a high-copy smt3 suppressor [7].
• The role of yeast UBC9 in cell cycle progression may thus be mediated through its SMT3 conjugation activity [4].

Anatomical context of SMT3

• We find that the conjugation machinery is required for lipopolysaccharide-induced expression of antimicrobial peptides in cultured cells and larvae, suggesting that Smt3 regulates Dorsal function in vivo [8].
• However, Smt3p was primarily detected on the mother cell side of the septin ring [9].

Associations of SMT3 with chemical compounds

• In this report, we show that Smt3 conjugation occurs at a single site in Dorsal (lysine 382), requires just the Smt3-activating and -conjugating enzymes, and is reversed by the deconjugating enzyme Ulp1 [8].

Physical interactions of SMT3

• A subset of these Smt3p-modified proteins co-immunoprecipitated with the septin Cdc11p [9].
• Segregation of the 2 microm circle requires two plasmid-encoded proteins, Rep1 and Rep2, which were found to colocalize with Ulp1 protein in the nucleus and interact with Smt3 in a two-hybrid assay [10].

Other interactions of SMT3

• Inactivation of Ulp2 also suppresses several ulp1(ts) defects, and the double mutant accumulates far fewer Smt3-protein conjugates than either single mutant [11].
• Smt3/SUMO and Ubc9 are required for efficient APC/C-mediated proteolysis in budding yeast [6].
• Yeast Smt3 and its vertebrate homolog SUMO-1 are ubiquitin-like proteins (Ubls) that are reversibly ligated to other proteins [11].
• Around the time of cytokinesis the Cdc3-Smt3 conjugate disappeared [12].
• The level of this modification was affected by Smt3-specific protease mutation ulp1-ts or overexpression of ULP1 [13].

Analytical, diagnostic and therapeutic context of SMT3

• Ligation of the ubiquitin-like protein SUMO (Smt3p) to other proteins is essential for viability of the yeast Saccharomyces cerevisiae [14].
• Immunofluorescence analysis showed prominent Smt3p SUMO localization at bud necks and sites of septum formation in hyphae similar to the septins [9].

References