Open AccessInhibition of Human Chk1 Causes Increased Initiation of DNA Replication, Phosphorylation of ATR Targets, and DNA Breakage
Author(s) -
Randi G. Syljuåsen,
Claus Storgaard Sørensen,
Lasse Tengbjerg Hansen,
Kasper Fugger,
Cecilia Lundin,
Fredrik Johansson,
Thomas Helleday,
Maxwell Sehested,
Jiří Lukáš,
Jiří Bártek
Publication year - 2005
Publication title -
molecular and cellular biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.14
H-Index - 327
eISSN - 1067-8824
pISSN - 0270-7306
DOI - 10.1128/mcb.25.9.3553-3562.2005
Subject(s) - biology , chek1 , dna replication , dna re replication , eukaryotic dna replication , control of chromosome duplication , s phase , microbiology and biotechnology , replication protein a , small interfering rna , g2 m dna damage checkpoint , dna damage , origin recognition complex , dna , cell cycle , biochemistry , cell cycle checkpoint , dna binding protein , rna , cell , gene , transcription factor
Human checkpoint kinase 1 (Chk1) is an essential kinase required to preserve genome stability. Here, we show that Chk1 inhibition by two distinct drugs, UCN-01 and CEP-3891, or by Chk1 small interfering RNA (siRNA) leads to phosphorylation of ATR targets. Chk1-inhibition triggered rapid, pan-nuclear phosphorylation of histone H2AX, p53, Smc1, replication protein A, and Chk1 itself in human S-phase cells. These phosphorylations were inhibited by ATR siRNA and caffeine, but they occurred independently of ATM. Chk1 inhibition also caused an increased initiation of DNA replication, which was accompanied by increased amounts of nonextractable RPA protein, formation of single-stranded DNA, and induction of DNA strand breaks. Moreover, these responses were prevented by siRNA-mediated downregulation of Cdk2 or the replication initiation protein Cdc45, or by addition of the CDK inhibitor roscovitine. We propose that Chk1 is required during normal S phase to avoid aberrantly increased initiation of DNA replication, thereby protecting against DNA breakage. These results may help explain why Chk1 is an essential kinase and should be taken into account when drugs to inhibit this kinase are considered for use in cancer treatment.