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Mol. Cell. Biol., May 1995, 2882-2892, Vol 15, No. 5
M Shimizu, E Ichikawa, U Inoue, T Nakamura, T Nakajima, H Nojima, H Okayama and K Oda
Multiple species of G1 cyclins and cyclin-dependent kinases are induced
sequentially during G1 phase, and the expression of cyclin A and cdc2 genes
is subsequently induced at the G1/S boundary. To analyze the mechanism of
cdc2 promoter activation, the 5'-flanking region of the rat cdc2 gene was
isolated and its structural features were characterized. The highly
conserved sequence between human and rat cdc2 genes is present in the basal
promoter region from positions -183 to - 122, which contains the E box,
SpI, and E2F motifs. The expression of 5' sequential deletion derivatives
of the promoter fused to luciferase cDNA in rat 3Y1 cells revealed the
presence of the enhancer element. The presumed enhancer region was further
analyzed by the introduction of base substitutions and by the formation of
DNA-protein complexes with cell extracts prepared at various times during
the G1-to-S-phase progression. These analyses revealed that the enhancer
sequence, AAGTTACAAATA, located from -276 to -265, confers strong
inducibility on the basal promoter at the G1/S boundary. The base
substitutions introduced into the motifs of transcription factors indicated
that the E2F motif is essential for the enhancer-dependent activation of
the cdc2 promoter at the G1/S boundary. Electrophoretic mobility shift
assays and DNase I footprinting showed that a factor which interacts with
the enhancer element is induced late in G1 phase.
Copyright © 1995, American Society for Microbiology
The G1/S boundary-specific enhancer of the rat cdc2 promoter
Department of Biological Science and Technology, Science University of Tokyo, Japan.
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