Fig. 7. CNBP positively regulates the endogenous expression of Myc. (A-D) Myc is normally abundantly expressed in the ANE at E7.25 (A) and in the neural folds (arrow, C) at E8.5, but is nearly undetectable in the neural folds (arrow, D) of Cnbp mutants. Expression in the allantois (arrowhead) is not affected in E8.5 mutant embryos. (E,F) At E9.5, Myc is expressed in the forebrain, as well as in the primitive facial prominences of wild-type embryos, but it was undetected in the anterior region of E9.5 mutant embryos. (G) CNBP upregulates Myc promoter activity in embryonic cells. Cnbp^+/+ and Cnbp^-/- mouse embryonic fibroblast cells (MEFs) were transfected with Myc promoter-luciferase plasmid (columns 1 and 2) or co-transfected with a mouse Cnbp-expression plasmid into Cnbp^-/- cells (column 3). A lower level of Myc expression was observed in Cnbp^-/- embryonic fibroblasts compared with Cnbp^+/+ cells. Transfection of Cnbp^-/- embryonic fibroblasts with the Cnbp-expression plasmid resulted in a Myc expression level higher than that found in Cnbp^+/+ cells. Results represent luciferase activity related to galactosidase activity. Values are the mean±s.d. of triplicate experiments.

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