DTL/CDT2 is essential for both CDT1 regulation and the early G2/M checkpoint.
Checkpoint genes maintain genomic stability by arresting cells after DNA damage. Many of these genes also control cell cycle events in unperturbed cells. By conducting a screen for checkpoint genes in zebrafish, we found that dtl/cdt2 is an essential component of the early, radiation-induced G2/M checkpoint. We subsequently found that dtl/cdt2 is required for normal cell cycle control, primarily to prevent rereplication. Both the checkpoint and replication roles are conserved in human DTL. Our data indicate that the rereplication reflects a requirement for DTL in regulating CDT1, a protein required for prereplication complex formation. CDT1 is degraded in S phase to prevent rereplication, and following DNA damage to prevent origin firing. We show that DTL associates with the CUL4-DDB1 E3 ubiquitin ligase and is required for CDT1 down-regulation in unperturbed cells and following DNA damage. The cell cycle defects of Dtl-deficient zebrafish are suppressed by reducing Cdt1 levels. In contrast, the early G2/M checkpoint defect appears to be Cdt1-independent. Thus, DTL promotes genomic stability through two distinct mechanisms. First, it is an essential component of the CUL4-DDB1 complex that controls CDT1 levels, thereby preventing rereplication. Second, it is required for the early G2/M checkpoint.
Sansam
Christopher L
CL
Center for Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Shepard
Jennifer L
JL
Lai
Kevin
K
Ianari
Alessandra
A
Danielian
Paul S
PS
Amsterdam
Adam
A
Hopkins
Nancy
N
Lees
Jacqueline A
JA
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000818:Animals; D018797:Cell Cycle Proteins / Q000378:metabolism*; D044842:Cullin Proteins / Q000378:metabolism; D004249:DNA Damage; D004268:DNA-Binding Proteins / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000002:abnormalities / Q000166:cytology / Q000528:radiation effects; D016195:G2 Phase / Q000502:physiology* / Q000528:radiation effects; D005820:Genetic Testing; D045325:HCT116 Cells; D006367:HeLa Cells; D006801:Humans; D008938:Mitosis / Q000502:physiology* / Q000528:radiation effects; D008954:Models, Biological; D016254:Mutagenesis, Insertional; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins; D011485:Protein Binding / Q000528:radiation effects; D011839:Radiation, Ionizing; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism; D015027:Zebrafish / Q000196:embryology / Q000378:metabolism*; D029961:Zebrafish Proteins / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; C467199:CDT1 protein, human; C114234:CUL4A protein, human; D018797:Cell Cycle Proteins; D044842:Cullin Proteins; C091435:DDB1 protein, human; D004268:DNA-Binding Proteins; C429530:DTL protein, human; C515646:DTL protein, zebrafish; D009687:Nuclear Proteins; D029961:Zebrafish Proteins; D044767:Ubiquitin-Protein Ligases