TABLE 2.

hCREG-mediated repression of E2F sites is context dependent^a

Promoter	Fold repression (± SEM) by hCREG in:
	Wild type	Mutant
DHFR	4.4 ± 0.1	1.9 ± 0.1
E2F1	2.5 ± 0.1	2.0 ± 0.3
b-myb	2.2 ± 0.1	1.9 ± 0.1

^aThe table presents the fold repression observed upon cotransfection with CMVhCREG relative to transfection with a control plasmid. For each promoter, “mutant” refers to the disruption of the E2F site(s). CV-1 cells on 6-cm plates were cotransfected with 2.5 μg of luciferase reporter and 2.5 μg of CMVhCREG, and the fold repression by hCREG was measured relative to the luciferase activity of the reporter with 2.5 μg of control DNA (CMVβgal). The activity of the DHFR mutant promoter was threefold lower than that of the wild type. The activity of the mutant b-myb promoter was twofold higher than that of the wild type, and the E2F1 mutant and wild-type promoters had comparable activities, a finding consistent with previous reports (37, 48). The values are the average from at least three experiments.