Ubiquitination and deubiquitination involved in cell cycle progression

摘要: The Anaphase-Promoting Complex/Cyclosome (APC/C) is a ubiquitin ligase that promotes degradation of mitotic regulators. Activation the APC/C requires either Cdc20 or Cdh1, together with phosphorylation. In chapter 2 this thesis, we show Polo-like kinase-1 (Plk1) required for activation Cdh1-dependent function during late mitosis. Plk1-depletion prevents dephoshorylation Cdh1. We found Plk1 mediates its effect on Cdh1 through phosphorylation phosphatase Cdc14A, which controls state conclude APC/CCdh1 activity hCdc14A, to ensure proper cell cycle progression. RASSF1C splice-variant Ras-association domain family gene. 3 describe identification consensus site Plk1-dependent in RASSF1C. can phosphorylate vitro and proteins interact vivo. Over-expression an active form reduces protein levels, whereas depletion increases level Importantly, interferes DNA damage-induced JNK-activation. Our data suggest novel role negatively regulating silence damage responses. To examine possible roles deubiquitinating enzymes (Dubs) G2/M progression, RNAi-based screen 4. By analyzing progression transfected cells, identified 6 Dubs appear have G2/M. Dub3 Usp35 seem be entry. Usp25 Usp30 play checkpoint-activity APC/C-inhibition. Usp8 Usp39 involved checkpoint cytokinesis. further focused phenotype induced by two independent shRNAs against Usp30. However, observed phenotypes did not correlate relative reduction mRNA, indicating off-target effects are Usp30-depletion phenotype. confirmed other hits RNA oligos. Thus, although emphasize risk effects, validity our 5 investigate showthat Dub3-depletion results G2 arrest. This arrest overcome early G2. inhibition after prolonged entry Dub3-depleted cells. find Plk1, downstream target G2-checkpoint, re-activated cells prolonged, Altogether, indicate recovery damage, possibly regulation Plk1. Accurate chromosome segregation relies spindle checkpoint, restricst until all chromosomes bipolarly attached. as new factor maintain support deprived Dub activity. consistent described mRNA processing, Aurora B-mRNA levels Usp39-depletion. observations splicing B mRNAs essential function.