Table 1.

Inhibition of DNA synthesis by antisense-cdc25C oligonucleotides in mid- and late-GI

Microinjection	No. of cells injected	Number of cell positive for BrdU	% cells inhibited
Sense cdc25C oligonucleotide S1 after 10 h	106	98	8
Sense cdc25C oligonucleotide S1 after 15 h	36	34	6
Antisense cdc25C oligonucleotide S1 after 10 h	168	17	90
Antisense cdc25C oligonucleotide S1 after 15 h	103	31	70

Background DNA synthesis was 97%. Hs68 fibroblasts were synchronized by serum starvation. In mid- and late-G1, at 10 or 15 h after the refeed, cells were microinjected with marker antibodies and sense (S1) or antisense oligonucleotide (AS1). After injection cells were further cultured in the presence of BrdU and fixed 22 h after refeeding. Subsequently, cells were stained for microinjection marker (to give the number of cells injected) and for DNA synthesis using anti-BrdU (to give the number of cells that have entered S-phase). None of the oligonucleotides inhibited DNA synthesis significantly when microinjected into S-phase cells, i.e., 18 to 22 h after the refeed. Numbers represent mean values of two to four independent experiments