The biosynthesis of DNA by insects: III. Ribonucleotide reductase activity and the effect of hydroxyurea during the adult development of the Cecropia silkworm

Abstract

Ribonucleotide reductase activity was examined in developing adults of the silkmoth Hyalophora cecropia. The experiments demonstrate, in vivo and in vitro, the incorporation of labeled ribonucleotides into DNA and the direct enzymatic reduction of labeled CMP by cell-free homogenates of tissues excised from developing adults. Hydroxyurea completely inhibits incorporation of labeled ribonucleotides into DNA in vivo, but does not affect the basal level of DNA synthesis or ribonucleotide reduction in vitro. Evidence is presented which indicates that hydroxyurea may prevent the allosteric activation of the reductase.