Over-expressed ZF5 gene product, a c-myc-binding protein related to GL1-Kruppel protein, has a growth-suppressive activity in mouse cell lines.

ZF5 encodes a zinc finger protein, which contains five C2H2-type zinc fingers showing homology with the zinc finger of the Kruppel family, and binds to two sites in the mouse c-myc promoter. We report the effect of over-expression of ZF5 on cell growth. ZnCl2 treatment suppressed the growth of a mouse fibroblast cell line (L cells) transfected with the wild-type ZF5 gene driven by the metallothionein promoter. Cells transfected with the wild-type ZF5 gene formed colonies two- to fivefold less efficiently than those transfected with the mutant ZF5 gene in P19, NIH3T3, 3T3-L1 and L cells. Over-expression of ZF5 did not cause c-myc down-regulation or arrest of the cell cycle, but increased the DNA content.