title: P90 RSK arranges Chk1 in the nucleus for monitoring of genomic integrity during cell proliferation.
abstract: The ataxia telangiectasia mutated- and rad3-related kinase (ATR)/Chk1 pathway is a sentinel of cell cycle progression. On the other hand, the Ras/mitogen-activated protein kinase/90-kDa ribosomal S6 kinase (p90 RSK) pathway is a central node in cell signaling downstream of growth factors. These pathways are closely correlated in cell proliferation, but their interaction is largely unknown. Here we show that Chk1 is phosphorylated predominantly at Ser-280 and translocated from cytoplasm to nucleus in response to serum stimulation. Nonphosphorylated Chk1-Ser-280 mutation attenuates nuclear Chk1 accumulation, whereas the phosphomimic mutation has a reverse effect on the localization. Treatment with p90 RSK inhibitor impairs Chk1 phosphorylation at Ser-280 and accumulation at the nucleus after serum stimulation, whereas these two phenomena are induced by the expression of the constitutively active mutant of p90 RSK in serum-starved cells. In vitro analyses indicate that p90 RSK stoichiometrically phosphorylates Ser-280 on Chk1. Together with Chk1 phosphorylation at Ser-345 by ATR and its autophosphorylation at Ser-296, which are critical for checkpoint signaling, Chk1-Ser-280 phosphorylation is elevated in a p90 RSK-dependent manner after UV irradiation. In addition, Chk1 phosphorylation at Ser-345 and Ser-296 after UV irradiation is also attenuated by the treatment with p90 RSK inhibitor or by Ser-280 mutation to Ala. These results suggest that p90 RSK facilitates nuclear Chk1 accumulation through Chk1-Ser-280 phosphorylation and that this pathway plays an important role in the preparation for monitoring genetic stability during cell proliferation.
authors.affiliation: Division of Biochemistry, Aichi Cancer Center Research Institute, 1-1 Kanokoden, Chikusa-Ku, Nagoya, Aichi 464-8681, Japan.
authors.forename: Ping
authors.initials: P
authors.lastname: Li
authors.forename: Hidemasa
authors.initials: H
authors.lastname: Goto
authors.forename: Kousuke
authors.initials: K
authors.lastname: Kasahara
authors.forename: Makoto
authors.initials: M
authors.lastname: Matsuyama
authors.forename: Zhonghua
authors.initials: Z
authors.lastname: Wang
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Yatabe
authors.forename: Tohru
authors.initials: T
authors.lastname: Kiyono
authors.forename: Masaki
authors.initials: M
authors.lastname: Inagaki
mesh_terms: D064007:Ataxia Telangiectasia Mutated Proteins; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism*; D049109:Cell Proliferation; D000071877:Checkpoint Kinase 1; D003593:Cytoplasm / Q000378:metabolism; D042822:Genomic Instability; D006367:HeLa Cells; D006801:Humans; D020935:MAP Kinase Signaling System; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010766:Phosphorylation; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D021381:Protein Transport; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering; D038744:Ribosomal Protein S6 Kinases, 90-kDa / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; D034741:RNA, Small Interfering; D011494:Protein Kinases; C576597:ATR protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D038744:Ribosomal Protein S6 Kinases, 90-kDa; D020928:Mitogen-Activated Protein Kinases