Showing papers by "Angelika Amon published in 1997"
TL;DR: Overexpression of either CDC20 or CDH1 was sufficient to induce APC-dependent proteolysis of the appropriate target in stages of the cell cycle in which substrates are normally stable.
Abstract: Proteolysis mediated by the anaphase-promoting complex (APC) triggers chromosome segregation and exit from mitosis, yet its regulation is poorly understood. The conserved Cdc20 and Cdh1 proteins were identified as limiting, substrate-specific activators of APC-dependent proteolysis. CDC20 was required for the degradation of the APC substrate Pds1 but not for that of other APC substrates, such as Clb2 and Ase1. Conversely, cdh1Δmutants were impaired in the degradation of Ase1 and Clb2 but not in that of Pds1. Overexpression of either CDC20 orCDH1 was sufficient to induce APC-dependent proteolysis of the appropriate target in stages of the cell cycle in which substrates are normally stable.
876 citations
TL;DR: A mutation com1-1 is identified, which blocks processing of meiotic double-strand breaks and which interferes with synaptonemal complex formation, homologous pairing and, as a consequence, spore viability after induction ofmeiotic recombination.
Abstract: We have designed a screen to isolate mutants defective during a specific part of meiotic prophase I of the yeast Saccharomyces cerevisiae. Genes required for the repair of meiotic double-strand breaks or for the separation of recombined chromosomes are targets of this mutant hunt. The specificity is achieved by selecting for mutants that produce viable spores when recombination and reductional segregation are prevented by mutations in SPO11 and SP013 genes, but fail to yield viable spores during a normal Rec + meiosis. We have identified and characterized a mutation com1-1 , which blocks processing of meiotic double-strand breaks and which interferes with synaptonemal complex formation, homologous pairing and, as a consequence, spore viability after induction of meiotic recombination. The COM1/SAE2 gene was cloned by complementation, and the deletion mutant has a phenotype similar to com1-1. com1/sae2 mutants closely resemble the phenotype of rad50S , as assayed by phase-contrast microscopy for spore formation, physical and genetic analysis of recombination, fluorescence in situ hybridization to quantify homologous pairing and immunofluorescence and electron microscopy to determine the capability to synapse axial elements.
219 citations
TL;DR: In budding yeast, stability of the mitotic B‐type cyclin Clb2 is tightly cell cycle‐regulated and Clb‐dependent kinases, when expressed during G1, are also capable of repressing the B‐ type cyclin proteolysis machinery.
Abstract: In budding yeast, stability of the mitotic B-type cyclin Clb2 is tightly cell cycle-regulated. B-type cyclin proteolysis is initiated during anaphase and persists throughout the G1 phase. Cln-Cdc28 kinase activity at START is required to repress B-type cyclin-specific proteolysis. Here, we show that Clb-dependent kinases, when expressed during G1, are also capable of repressing the B-type cyclin proteolysis machinery. Furthermore, we find that inactivation of Cln- and Clb-Cdc28 kinases is sufficient to trigger Clb2 proteolysis and sister-chromatid separation in G2/M phase-arrested cells, where the B-type cyclin-specific proteolysis machinery is normally inactive. Our results suggest that Cln- and Clb-dependent kinases are both capable of repressing B-type cyclin-specific proteolysis and that they are required to maintain the proteolysis machinery in an inactive state in S and G2/M phase-arrested cells. We propose that in yeast, as cells pass through START, Cln-Cdc28-dependent kinases inactivate B-type cyclin proteolysis. As Cln-Cdc28-dependent kinases decline during G2, Clb-Cdc28-dependent kinases take over this role, ensuring that B-type cyclin proteolysis is not activated during S phase and early mitosis.
88 citations