SCF(Fbxw7/hCdc4) targets cyclin E2 for ubiquitin-dependent proteolysis.
E-type cyclins (E1 and E2) regulate the S phase program in the mammalian cell division cycle. Expression of cyclin E1 and E2 is frequently deregulated in a variety of cancer types and a wealth of experimental evidence supports an oncogenic role of these proteins in human tumorigenesis. Although the molecular mechanisms responsible for cyclin E1 deregulation in cancer are well defined, little is known regarding cyclin E2. Here we report that cyclin E2 is targeted for ubiquitin-dependent proteolysis by the ubiquitin ligase SCF(Fbxw7/hCdc4). Ubiquitylation is triggered by phosphorylation of cyclin E2 on residues Thr392 and Ser396, and to a lesser extent Thr74, contained in two consensus Cdc4-phosphodegrons. Furthermore, we found that ectopic expression of cyclin E1 enhances the ubiquitin-dependent proteolysis of cyclin E2 in vivo, suggesting a potential cross-talk in the regulation of E-type cyclin activity. Since SCF(Fbxw7/hCdc4) is functionally inactivated in several human cancer types, alteration of this molecular pathway could contribute to the deregulation of cyclin E2 in tumorigenesis.
Klotz
Kathleen
K
Sidney Kimmel Cancer Center, 10905 Road to the Cure, San Diego, CA 92121, USA.
Cepeda
Diana
D
Tan
Yingmeei
Y
Sun
Dahui
D
Sangfelt
Olle
O
Spruck
Charles
C
D001665:Binding Sites; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000378:metabolism*; D045744:Cell Line, Tumor; D019927:Cyclin E / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D016213:Cyclins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D044783:F-Box Proteins / Q000378:metabolism*; D000073979:F-Box-WD Repeat-Containing Protein 7; D006367:HeLa Cells; D006801:Humans; D016297:Mutagenesis, Site-Directed; D009369:Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D015513:Oncogene Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D034622:RNA Interference; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012694:Serine / Q000737:chemistry; D013379:Substrate Specificity; D013912:Threonine / Q000737:chemistry; D025801:Ubiquitin / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*
C475820:CCNE1 protein, human; C503688:CCNE2 protein, human; D018797:Cell Cycle Proteins; D019927:Cyclin E; D016213:Cyclins; D044783:F-Box Proteins; D000073979:F-Box-WD Repeat-Containing Protein 7; C513273:FBXW7 protein, human; D015513:Oncogene Proteins; D011994:Recombinant Proteins; D025801:Ubiquitin; D013912:Threonine; D012694:Serine; D044767:Ubiquitin-Protein Ligases