The negative regulation of p27 by Skp2 involves into cell cycle transition, and contributes to DOX resistance, Radiation resistance, Troglitazone resistance, Actinomycin D resistance and Paclitaxel resistance. Black arrows indicate different signaling pathways. P: phosphorylation; Ac: Acetlation; Ub, Ubiquitiantion. PIRH2: p53-induced RING-H2, KPC: Kip1 ubiquitylation-promoting complex, Cks1: cyclin kinase subunit 1, PCAF: p300/CBP-associated factor, MEF2: Myocyte enhancer factor 2, GSK-3β: glycogen synthase kinase 3 beta, hMOF: KAT8 or MYST1, CENP-A: centromere protein-A, MAD2: mitotic arrest deficient 2, NOTCH1: Notch homolog 1.