I've found this article, which is a very old one (from the time when nucleoside analogs where researched as a possible way to prevent replication of virus genetic material, before the HIV epidemics). In the last page, the authors suggest that cellular repair enzymes could remove azidothymidine (AZT, zidovudine) from cellular DNA if it's incorporated, but viruses' polymerases lack this ability. As it's an old article, I would like to know if this hypothesis was confirmed. As both azidothymidine and thymidine can form normal base pairings, how could human enzymes detect an azidothymidine was incorporated?
If someone is not familiar with AZT mechanism: basically, it's an analog of thymidine which has an azide group instead of 3'-OH
It can be phosphorylated by cell kinases and incorporated to the growing DNA chain; however, this will stop the polymerization because it depends on free 3'-OH. The natural question which follows is: why wouldn't AZT also block the replication of human cells' DNA?