"Securin, like mitotic cyclins, is the target of the anaphase promoting complex (APC)/cyclosome and is polyubiquitinated before destruction in a manner dependent upon the destruction sequence."

"The anaphase never occurs properly in the absence of securin destruction."

"Our data increase the total number of identified APC subunits to 13 in both yeasts and indicate that previous approaches were biased against the identification of small subunits."

"APC/C's RING finger is located within the small subunit Apc11, which by itself has the properties of a minimal ubiquitin ligase ( 13 , 22 )."

"Apc11 is anchored to the complex through Apc2, a subunit distantly related to cullins ( 50 , 54 )."

"Accordingly, purification of a TAP-tagged version of Apc13 yielded the same set of APC/C subunits as Cut9-TAP (Fig. 2C ), demonstrating that apc13 + encodes a subunit of the fission yeast APC/C."

"Here, we provide evidence that the Saccharomyces cerevisiae RING-H2 finger protein Apc11 defines the minimal ubiquitin ligase activity of the APC."

"Using purified, recombinant proteins we showed that Apc11p interacted directly with the Ubc4 ubiquitin conjugating enzyme (E2)."

"However, Apc11p bearing mutations in putative metal-binding cysteines (C41, C44, or C91) showed little or no activity in this assay (Figure 5 A, lanes 3, 4, and 9), demonstrating that the RING-H2 finger is absolutely required for its E3 activity."

"Our work, and that of others, indicates that RING-based E3s do not act as ubiquitin carriers that form thioester intermediates, but instead act as bridges between E2s and substrates that provide a favorable environment for the transfer of ubiquitin."

"In combination with Ubc4 or UbcH10, a heterodimeric complex of APC2 and APC11 is sufficient to catalyze the ubiquitination of human securin and cyclin B1."

"However, the minimal APC2/11 ubiquitin ligase module does not possess substrate specificity, because it also ubiquitinates the destruction box deletion mutants of securin and cyclin B1."

"Both APC11 and UbcH10 bind to the C-terminal cullin homology domain of APC2, whereas Ubc4 interacts with APC11 directly."

"The rapid degradation of Cut2 at anaphase requires its amino-terminal region and the activity of Cut9 (ref. 14), a component of the 20S cyclosome/anaphase-promoting complex (APC), which is necessary for cyclin destruction."

"Mitotic progression is driven by proteolytic destruction of securin and cyclins. These proteins are labeled for destruction by an ubiquitin-protein isopeptide ligase (E3) known as the anaphase-promoting complex or cyclosome (APC/C)."

"The APC/C requires activators (Cdc20 or Cdh1) to efficiently recognize its substrates, which are specified by destruction (D box) and/or KEN box signals."

"The APC/C becomes active at the metaphase/anaphase transition and remains active during G(1) phase."

"We determined the essentiality of 4,836 genes by sporulating each heterozygous deletion diploid strain followed by microscopic observation of the germinating haploid spores."

"In brief, 0.05 mg/ml Uba1, 0.5mg/ml E2s (ubc1, ubc4 and ubc11) and 0.3 mM ATP were mixed with 1.5 mg/ml wild-type mono-ubiquitin (Sigma Aldrich), 2μM ubiquitin aldehyde (Boston Biochem) in a ubiquitination buffer containing 25 mM HEPES pH 7.5, 100 mM KCl, 3mM ATP, 2.5 mM MgCl2, and 0.2 mM DTT."

"APC/C ubiquitylated a Cdc2–Cdc13 substrate in an E1-, E2-, and ATP-dependent assay, while cellular APC/C activity generated ubiquitylated Cut2."

"Apc11, Apc2, and Apc10 occupy the catalytic side of the assembly, spatially separated from much of the TPR scaffold."

"Ubc11 can generate short ubiquitin chains in the absence of Ubc4, whereas Ubc4 cannot ubiquitylate APC/C substrates without Ubc11, supporting a model in which Ubc11 participates in initial substrate modification and Ubc4 supports chain extension."

"The APC/C is composed of at least 13 subunits: apc1, apc2,"