title: SP600125 suppresses Cdk1 and induces endoreplication directly from G2 phase, independent of JNK inhibition.
abstract: Cell cycle controls ensure that DNA replication (S phase) follows mitosis resulting in two precise copies of the genome. A failure of the control mechanisms can result in multiple rounds of DNA replication without cell division. In endoreplication, cells with replicated genomes bypass mitosis, then replicate their DNA again, resulting in polyploidy. Endoreplication from G2 phase lacks all hallmarks of mitosis. Using synchronized cells, we show that the c-Jun N-terminal kinase (JNK) inhibitor, SP600125, prevents the entry of cells into mitosis and leads to endoreplication of DNA from G2 phase. We show that cells proceed from G2 phase to replicate their DNA in the absence of mitosis. This effect of SP600125 is independent of its suppression of JNK activity. Instead, the inhibitory effect of SP600125 on mitotic entry predominantly occurs upstream of Aurora A kinase and Polo-like kinase 1, resulting in a failure to remove the inhibitory phosphorylation of Cdk1. Importantly, our results directly show that the inhibition of Cdk1 activity and the persistence of Cdk2 activity in G2 cells induces endoreplication without mitosis. Furthermore, endoreplication from G2 phase is independent of p53 control.
authors.affiliation: Sidney Kimmel Cancer Center, San Diego, CA, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Kim
authors.forename: J
authors.initials: J
authors.lastname: Lee
authors.forename: R L
authors.initials: RL
authors.lastname: Margolis
authors.forename: R
authors.initials: R
authors.lastname: Fotedar
mesh_terms: D000873:Anthracenes / Q000494:pharmacology*; D064127:Aurora Kinases; D015153:Blotting, Western; D016203:CDC2 Protein Kinase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D019926:Cyclin B / Q000378:metabolism; D051357:Cyclin-Dependent Kinase 2 / Q000378:metabolism; D004261:DNA Replication / Q000187:drug effects*; D004789:Enzyme Activation / Q000187:drug effects; D005434:Flow Cytometry; D016195:G2 Phase / Q000187:drug effects* / Q000235:genetics / Q000502:physiology; D045325:HCT116 Cells; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D008938:Mitosis / Q000187:drug effects; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D034622:RNA Interference; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D000097869:Polo-Like Kinase 1
chemical_list: D000873:Anthracenes; D064127:Aurora Kinases; D016203:CDC2 Protein Kinase; D018797:Cell Cycle Proteins; D019926:Cyclin B; D051357:Cyclin-Dependent Kinase 2; D048031:JNK Mitogen-Activated Protein Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D016159:Tumor Suppressor Protein p53; D000097869:Polo-Like Kinase 1; C432165:pyrazolanthrone