The effects of an RNase H-active, chimeric methylphosphonodiester / phosphodiester antisense oligodeoxynucleotide on c-myc mRNA and c-Myc protein in KYO1 cells. (A) Relative levels of mRNA and protein at 4 h post intracytoplasmic delivery by streptolysin O permeabilization were determined by densitometry of Northern and Western blots. Data represent the mean and standard deviation of 3 replicates. The structures of the antisense oligodeoxynucleotide, and inverted antisense and sense controls are given in Table 1. (B) Northern blots of c-myc mRNA at 4 h following oligodeoxynucleotide delivery by streptolysin O permeabilization and by electroporation of KYO1 cells. Grey arrow; full length mRNA. Black arrows; RNase H-generated 5' fragments of mRNA.