title: Suppression of Tousled-like kinase activity after DNA damage or replication block requires ATM, NBS1 and Chk1.
abstract: The human Tousled-like kinases 1 and 2 (TLK) have been shown to be active during S phase of the cell cycle. TLK activity is rapidly suppressed by DNA damage and by inhibitors of replication. Here we report that the signal transduction pathway, which leads to transient suppression of TLK activity after the induction of double-strand breaks (DSBs) in the DNA, is dependent on the presence of a functional ataxia-telangiectasia-mutated kinase (ATM). Interestingly, we have discovered that rapid suppression of TLK activity after low doses of ultraviolet (UV) irradiation or aphidicolin-induced replication block is also ATM-dependent. The nature of the signal that triggers ATM-dependent downregulation of TLK activity after UVC and replication block remains unknown, but it is not due exclusively to DSBs in the DNA. We also demonstrate that TLK suppression is dependent on the presence of a functional Nijmegan Breakage Syndrome protein (NBS1). ATM-dependent phosphorylation of NBS1 is required for the suppression of TLK activity, indicating a role for NBS1 as an adaptor or scaffold in the ATM/TLK pathway. ATM does not phosphorylate TLK directly to regulate its activity, but Chk1 does phosphorylate TLK1 GST-fusion proteins in vitro. Using Chk1 siRNAs, we show that Chk1 is essential for the suppression of TLK activity after replication block, but that ATR, Chk2 and BRCA1 are dispensable for TLK suppression. Overall, we propose that ATM activation is not linked solely to DSBs and that ATM participates in initiating signaling pathways in response to replication block and UV-induced DNA damage.
authors.affiliation: Signal Transduction Lab, Cancer and Cell Biology Division, Queensland Institute of Medical Research, 300 Herston Rd, Qld 4029, Australia. darrenk@qimr.edu.au
authors.forename: Darren R
authors.initials: DR
authors.lastname: Krause
authors.forename: Jyoti C
authors.initials: JC
authors.lastname: Jonnalagadda
authors.forename: Magtouf H
authors.initials: MH
authors.lastname: Gatei
authors.forename: Herman H W
authors.initials: HH
authors.lastname: Sillje
authors.forename: Bin-Bing
authors.initials: BB
authors.lastname: Zhou
authors.forename: Erich A
authors.initials: EA
authors.lastname: Nigg
authors.forename: Kumkum
authors.initials: K
authors.lastname: Khanna
mesh_terms: D016590:Aphidicolin / Q000494:pharmacology; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D002478:Cells, Cultured; D000071877:Checkpoint Kinase 1; D004249:DNA Damage / Q000502:physiology*; D004261:DNA Replication / Q000187:drug effects / Q000528:radiation effects; D004268:DNA-Binding Proteins; D004307:Dose-Response Relationship, Radiation; D004789:Enzyme Activation / Q000187:drug effects / Q000528:radiation effects; D005720:Gamma Rays; D005982:Glutathione Transferase / Q000235:genetics / Q000378:metabolism; D006801:Humans; D009687:Nuclear Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D010766:Phosphorylation; D011494:Protein Kinases / Q000187:drug effects / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D017346:Protein Serine-Threonine Kinases / Q000187:drug effects / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D034741:RNA, Small Interfering / Q000494:pharmacology; D011839:Radiation, Ionizing; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012694:Serine / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000528:radiation effects; D025521:Tumor Suppressor Proteins; D014466:Ultraviolet Rays
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C112156:NBN protein, human; D009687:Nuclear Proteins; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; D025521:Tumor Suppressor Proteins; D016590:Aphidicolin; D012694:Serine; D005982:Glutathione Transferase; D011494:Protein Kinases; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1; D017346:Protein Serine-Threonine Kinases; C425323:TLK1 protein, human