title: Loss of RPA1 induces Chk2 phosphorylation through a caffeine-sensitive pathway.
abstract: RPA is an important component of DNA replication, repair and recombination, but its involvement in the signaling of cell-cycle checkpoints is not well understood. In this study, we show that knockdown of RPA1 by siRNA duplexes induces ATM (Ser1981) and Chk2 (Thr68), but not Chk1 (Ser345) phosphorylation and results in p21 upregulation in HeLa cells. However, the induction of Chk2 (Thr68) phosphorylation and p21 expression by RPA1 siRNA transfection can be completely blocked by the ATM inhibitor caffeine. Moreover, transfection of siRNAs targeting ATM dramatically reduces Chk2 (Thr68) phosphorylation in RPA1 knockdown cells. Taken together, these results suggest that loss of RPA1 activates the Chk2 signaling pathway in an ATM-dependent manner.
authors.affiliation: Drug Discovery Program, H. Lee Moffitt Cancer Center and Research Institute 12902 Magnolia Drive, Tampa, FL 33612, USA.
authors.forename: Runa
authors.initials: R
authors.lastname: Araya
authors.forename: Itaru
authors.initials: I
authors.lastname: Hirai
authors.forename: Cheryl L
authors.initials: CL
authors.lastname: Meyerkord
authors.forename: Hong-Gang
authors.initials: HG
authors.lastname: Wang
mesh_terms: D064007:Ataxia Telangiectasia Mutated Proteins; D001483:Base Sequence; D002110:Caffeine / Q000494:pharmacology*; D018797:Cell Cycle Proteins; D000071877:Checkpoint Kinase 1; D064447:Checkpoint Kinase 2; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D010766:Phosphorylation / Q000187:drug effects; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000502:physiology*; D034741:RNA, Small Interfering / Q000235:genetics; D051716:Replication Protein A; D025521:Tumor Suppressor Proteins
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D034741:RNA, Small Interfering; C497167:RPA1 protein, human; D051716:Replication Protein A; D025521:Tumor Suppressor Proteins; D002110:Caffeine; D011494:Protein Kinases; D064447:Checkpoint Kinase 2; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C000605867:CHEK1 protein, human; C578634:CHEK2 protein, human; D000071877:Checkpoint Kinase 1; D017346:Protein Serine-Threonine Kinases