Effect of tumor suppressors on cell cycle-regulatory genes: RB suppresses p34cdc2 expression and normal p53 suppresses cyclin A expression.
We show that expression of the p34cdc2 and cyclin A genes is induced by interleukin-2 in normal human T cells and present evidence to support the idea that these genes are deregulated in leukemic T cells. Our DNA sequencing data indicate that the promoter region of the p34cdc2 gene contains putative E2F-like binding sites which are recognized by Rb and binding sites for c-myb, Sp1, and ATF, and that the promoter region of the cyclin A gene contains binding sites for p53, Sp1, and ATF. In this study we focus on the effect of p53 and Rb on these cell cycle-regulatory genes. Cotransfection of Y79 human retinoblastoma cells with a p34cdc2 promoter-luciferase expression vector and a plasmid expressing the retinoblastoma gene (RB) indicated that RB suppresses p34cdc2 expression. Cotransfection of B104 rat neuroblastoma cells with a cyclin A promoter-luciferase expression vector and a plasmid expressing the normal or mutant p53 indicated that only the normal p53 suppresses cyclin A expression. In normal T cells, PHA stimulation reduces the amount of complexes in the p34cdc2 promoter between the E2F-like binding site and the RB gene product. These complexes were not detected in leukemic T cells. Our data support the idea that tumor suppressors modulate the expression of cell cycle-regulatory genes: RB regulates p34cdc2 expression and p53 regulates cyclin A expression.
Yamamoto
M
M
Wistar Institute of Anatomy and Biology, Philadelphia, Pennsylvania 19104.
Yoshida
M
M
Ono
K
K
Fujita
T
T
Ohtani-Fujita
N
N
Sakai
T
T
Nikaido
T
T
D001483:Base Sequence; D016203:CDC2 Protein Kinase / Q000235:genetics*; D002453:Cell Cycle; D002478:Cells, Cultured; D016213:Cyclins / Q000235:genetics*; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D066298:In Vitro Techniques; D007376:Interleukin-2 / Q000494:pharmacology; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics; D016160:Retinoblastoma Protein / Q000502:physiology*; D017384:Sequence Deletion; D013601:T-Lymphocytes / Q000502:physiology; D016159:Tumor Suppressor Protein p53 / Q000502:physiology*
D016213:Cyclins; D004268:DNA-Binding Proteins; D007376:Interleukin-2; D012333:RNA, Messenger; D016160:Retinoblastoma Protein; D016159:Tumor Suppressor Protein p53; D016203:CDC2 Protein Kinase