The tumour suppressor protein p53 can repress transcription of cyclin B.
The tumour suppressor protein p53 has functions in controlling the G(1)/S and G(2)/M transitions. Central regulators for progression from G(2) to mitosis are B-type cyclins complexed with cdc2 kinase. In mammals two cyclin B proteins are found, cyclin B1 and B2. We show that upon treatment of HepG2 cells with 5-fluorouracil or methotrexate, p53 levels increase while concentrations of cyclin B2 mRNA, measured by RT-PCR with the LightCycler system, are reduced. In DLD-1 colorectal adenocarcinoma cells (DLD-1-tet-off-p53) cyclin B1 and B2 mRNA levels drop after expression of wild-type p53 but not after induction of a DNA binding-deficient mutant of p53. Analysis of the cyclin B2 promoter reveals specific repression of this gene by p53. Transfection of wild-type p53 into SaOS-2 cells shuts off transcription from a cyclin B2 promoter-luciferase construct whereas a p53 mutant protein does not. The cyclin B2 promoter does not contain a consensus p53 binding site. Most of the p53-dependent transcriptional responsiveness resides in its 226 bp core promoter. Taken together with earlier observations on p53-dependent transcription of cyclin B1, our results suggest that one way of regulating G(2) arrest may be a reduction in cyclin B levels through p53-dependent transcriptional repression.
Krause
K
K
Medizinische Klinik II, Max Bürger Forschungszentrum, Universität Leipzig, Johannisallee 30, D-04103 Leipzig, Germany.
Wasner
M
M
Reinhard
W
W
Haugwitz
U
U
Dohna
C L
CL
Mössner
J
J
Engeland
K
K
D019926:Cyclin B / Q000235:genetics*; D056744:Cyclin B1; D056765:Cyclin B2; D005472:Fluorouracil / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D008727:Methotrexate / Q000494:pharmacology; D009154:Mutation; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000502:physiology*
C534699:CCNB1 protein, human; C503758:CCNB2 protein, human; D019926:Cyclin B; D056744:Cyclin B1; D056765:Cyclin B2; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D016159:Tumor Suppressor Protein p53; D008156:Luciferases; D005472:Fluorouracil; D008727:Methotrexate