Nature of the Zn2+ requirement for DNA synthesis by 3T3 cells

Transit of 3T3 cells from quiescence to S phase requires an adequate supply of Zn2+ during the second half of the transition. The nature of this requirement has been investigated. Completion of the Zn2(+)-dependent process required ongoing mRNA and protein synthesis but could be accomplished in serum-free medium. Combination of low Zn2+ availability with inhibition of mRNA synthesis by 5,6-dichlororibofuranosylbenzimidazole or of protein synthesis by cycloheximide resulted in the cells almost completely reverting to a quiescent state. The results suggest that Zn2+ is required for the accumulation and maintenance of a protein involved in the progression of untransformed cells into S phase.