A second human Dbf4/ASK-related protein, Drf1/ASKL1, is required for efficient progression of S and M phases.
Cdc7-Dbf4 kinase is conserved through evolution and regulates initiation and progression of DNA replication. In human, ASK/hsDbf4 binds and activates huCdc7 during S phase and this kinase complex is essential for DNA replication and cell proliferation. Drf1/ASKL1, a second human Dbf4/ASK-related protein, shares three conserved Dbf4 motifs previously identified on all of the Dbf4-related molecules. Drf1/ASKL1 can bind and activate huCdc7, and Cdc7-ASKL1 complex phosphorylates MCM2. ASKL1 transcription and protein levels oscillate during cell cycle and increase at late S to G2/M phases. The protein is detected predominantly in the nuclear-soluble fraction but not in the chromatin-bound fraction. Inhibition of Drf1/ASKL1 expression by siRNA results in attenuation of cell growth and in the increase of late S and G2/M phase population. siRNA treatment on synchronized cell population revealed that S phase progression is delayed when ASKL1 protein level is decreased. S phase delay may be linked to replication fork block, because increased levels of gammaH2AX and activated form of Chk2 are detected with ASKL1 siRNA in the absence of any additional DNA damages. Furthermore, mitotic progression is retarded in ASKL1 or Cdc7 siRNA-treated cells. Our results suggest that ASKL1 in a complex with Cdc7 may play a role in normal progression of both S and M phases.
Yoshizawa-Sugata
Naoko
N
Department of Cell Biology, Tokyo Metropolitan Institute of Medical Science, Tokyo 113-8613, Japan.
Ishii
Ai
A
Taniyama
Chika
C
Matsui
Etsuko
E
Arai
Ken-ichi
K
Masai
Hisao
H
D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry / Q000502:physiology*; D020816:Amino Acid Motifs; D001973:Bromodeoxyuridine / Q000494:pharmacology; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D002455:Cell Division; D002467:Cell Nucleus / Q000378:metabolism; D049109:Cell Proliferation; D004247:DNA / Q000378:metabolism; D004249:DNA Damage; D004261:DNA Replication; D003902:Detergents / Q000494:pharmacology; D000080865:Formins; D016195:G2 Phase; D005982:Glutathione Transferase / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D064111:Minichromosome Maintenance Complex Component 2; D008938:Mitosis; D015739:Nocodazole / Q000494:pharmacology; D009687:Nuclear Proteins / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D016196:S Phase; D013347:Subcellular Fractions; D013936:Thymidine / Q000737:chemistry; D013997:Time Factors; D014158:Transcription, Genetic; D014162:Transfection
D048868:Adaptor Proteins, Signal Transducing; D018797:Cell Cycle Proteins; C485678:DBF4 protein, human; C108962:DIAPH1 protein, human; D003902:Detergents; D000080865:Formins; D009687:Nuclear Proteins; D034741:RNA, Small Interfering; D004247:DNA; D008156:Luciferases; D005982:Glutathione Transferase; C068619:CDC7 protein, human; D017346:Protein Serine-Threonine Kinases; D064111:Minichromosome Maintenance Complex Component 2; D001973:Bromodeoxyuridine; D015739:Nocodazole; D013936:Thymidine