title: Cyclin A regulates a cell-cycle-dependent expression of CKAP2 through phosphorylation of Sp1.
abstract: CKAP2 plays crucial roles in proper chromosome segregation and maintaining genomic stability. CKAP2 protein showed cell-cycle-dependent expression, which reached a maximum level at the G2/M phase and disappeared at the onset of G1 phase. To elucidate the mechanisms underlying cell cycle-dependent expression of CKAP2, we cloned and analyzed the human CKAP2 promoter. The upstream 115-bp region from the transcription start site was sufficient for minimal CKAP2 promoter activity. We identified 2 regulatory sequences; a CHR (-110 to -104 bp) and a GC box (-41 to -32 bp). We confirmed Sp1 bound to the GC box using a supershift assay and a ChIP assay. Mutation in the GC box resulted in a near complete loss of CKAP2 promoter activity while mutation in the CHR decreased the promoter activity by 50%. The CHR mutation showed enhanced activity at the G1/S phase, but still retained cyclic activity. The Chromatin IP revealed that the amount of Sp1 bound to the GC box gradually increased and reached a maximum level at the G2/M phase. The amount of Sp1 bound to the GC box was greatly reduced when Cyclin A was depleted, which was restored by adding Cyclin A/Cdk2 complex back into the nuclear extracts. Together, we concluded that the GC box was responsible for the cyclic activity of human CKAP2 promoter through the phosphorylation of Sp1, possibly by Cyclin A/Cdk complex.
authors.affiliation: Department of Molecular Cell Biology and Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, 300 Chunchundong, Jangangu, Suwon 440-746, Republic of Korea.
authors.forename: Du-Seock
authors.initials: DS
authors.lastname: Kang
authors.forename: Kyeong-Man
authors.initials: KM
authors.lastname: Hong
authors.forename: Joobae
authors.initials: J
authors.lastname: Park
authors.forename: Chang-Dae
authors.initials: CD
authors.lastname: Bae
mesh_terms: D002453:Cell Cycle / Q000235:genetics*; D019925:Cyclin A / Q000378:metabolism*; D003598:Cytoskeletal Proteins / Q000235:genetics*; D005786:Gene Expression Regulation; D006801:Humans; D011401:Promoter Regions, Genetic; D016329:Sp1 Transcription Factor / Q000378:metabolism*
chemical_list: C114988:CKAP2 protein, human; D019925:Cyclin A; D003598:Cytoskeletal Proteins; D016329:Sp1 Transcription Factor