This SpringerBrief explores thephysiological roles ofSkp1-Cullin1-F-box Complex(SCF) andAnaphase Promoting Complex (APC) in normal cells and in tumor formation. These tworelated, multi-subunit E3 ubiquitin ligase enzymes, APCandSCFare thought to be the major driving forces governing proper cell cycle progression.Defective cell cycle regulation leads to genomic instability and ultimately, cancer development. Selective degradation of key cell cycle regulators by the ubiquitin-proteasome system has been proven to be a major regulatory mechanism for ensuring ordered and coordinated cell cycle...