Alkali lability of deoxyribonucleic acid that contains adenine arabinoside

We have demonstrated previously that 9-beta-D-arabinofuranosyl adenosine (ara-A), like 1-beta-D-arabinofuranosyl cytosine (ara-C), incorporates exclusively into DNA, not RNA [Kufe et al., Cancer Res. 43, 2000 (1983)]. We have also demonstrated that (ara-C)DNA is degraded by alkali [Major et al., Biochem. Pharmac. 31, 861 (1982)], suggesting a structural instability of this abnormal nucleic acid. These findings have been extended by investigating the effects of various alkaline conditions on ara-A and (ara-A)DNA. The results indicate that the nucleoside was degraded under stringent conditions (0.4 M NaOH, 0.5 hr, 100 degrees) and that a similar effect occurred following exposure of (ara-A)DNA. The results also indicate that milder alkaline conditions (0.4 M NaOH, 6 hr, 37 degrees) resulted in strand scission of (ara-A)DNA at the 3'-carbon of the incorporated arabinosyl sugar without degradation of the ara-A moiety itself. These findings may be useful when attempting to purify (ara-A)DNA and confirm the structural instability of arabinosyl-containing DNA.