Ribonucleotides are not channeled into DNA in permeabilized mammalian cells

Reddy and Pardee earlier reported that permeabilized CHEF/18 cells (J. Biol. Chem 257, 12526) or soluble extracts from such cells (Cell 32, 443) under the proper conditions preferentially incorporated a labeled ribonucleotide (CDP) into DNA without dilution by an excess of non-labeled dCTP, suggesting channeling of ribonucleotides into DNA by a multiprotein complex. Here we present results suggesting that in these experiments CDP was incorporated into RNA and not into DNA.