Cdk2-dependent phosphorylation of the NF-Y transcription factor is essential for the expression of the cell cycle-regulatory genes and cell cycle G1/S and G2/M transitions.
We previously reported that cdk2 phosphorylates two serine residues near the DNA-binding domain of the YA subunit of NF-Y transcription factor and this phosphorylation is essential for DNA binding of NF-Y. In this study, we examined the effects of a phosphorylation-deficient mutant form of YA, YA-aa, in which the two serine residues are replaced with alanine, on the cell cycle and expression of the NF-Y target genes. Transient transfection assays show that YA-aa inhibits transcription from the NF-Y target promoters, such as cdc2, cyclin A, and cdc25C. Moreover, this inhibitory function of YA-aa can be suppressed by the expression of wild-type YA, implying that YA-aa inhibits transcription of those NF-Y target genes by inactivating wild-type YA. Since NF-Y target genes include the cell cycle-regulatory genes that ensure orderly progression of the cell cycle, we examined the effects of YA-aa in cell cycle progression. We constructed a recombinant adenovirus encoding YA-aa and found that YA-aa expression leads to repression of cell cycle-regulatory genes, such as cyclin A, RNR R2, DNA polymerase alpha, cdc2, cyclin B, and cdc25C. Consistently, YA-aa expression results in the inactivation of both cdc2 and cdk2. Furthermore, cell cycle analysis reveals that YA-aa induces cell cycle arrest at both G1 and G2/M. These results suggest that cdk2-dependent phosphorylation of NF-Y is essential for the expression of the cell cycle-regulatory genes and therefore for cell cycle progression at both G1/S and G2/M.
Chae
Hee-Don
HD
National Research Laboratory, Department of Microbiology, Dankook University College of Medicine, Cheonan 330-714, Korea.
Yun
Jeanho
J
Bang
Yung-Jue
YJ
Shin
Deug Y
DY
D000256:Adenoviridae; D023081:CCAAT-Binding Factor / Q000235:genetics / Q000378:metabolism*; D042846:CDC2-CDC28 Kinases / Q000378:metabolism*; D002453:Cell Cycle / Q000235:genetics / Q000502:physiology*; D051357:Cyclin-Dependent Kinase 2; D018014:Gene Transfer Techniques; D018816:Genes, cdc; D005822:Genetic Vectors; D006801:Humans; D010766:Phosphorylation
D023081:CCAAT-Binding Factor; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2