Figure 5.

(A) Mismatch repair activity in extracts of tumor cell lines treated with 5′-aza 2′-deoxycytidine. Repair reactions were incubated for 30 min (except G⋅G-3′ for 15 min), and the products were analyzed as described in Materials and Methods. Results are for the mismatched substrates G⋅G-5′/3′ and 2 unpaired bases with a nick 5′ to unpaired bases. DNA substrates contained a nick in the minus strand at either position −264 (for the 3′ nicked substrate) or at position +276 (for the 5′ nicked substrate), where position +1 is the first transcribed base of the lacZα-complementation gene. The G⋅G mismatch is at position 88, and α2 is at 90, 91 of the lacZα gene. HeLa, RKO-pretreatment (RKO-Pre), and SW48-pretreatment (SW48-Pre) are compared with cell extracts of RKO (RKO-5-AzaC) and SW48 (SW48-5-AzaC) made after 5 days of treatment with 5-aza-2′-deoxycytidine. (B) Mismatch repair activity in extracts of the AN3CA tumor cell line either untreated or treated with 5′ azacytidine. Above described substrates are tested in AN3CA cell extracts either pre, 1 day, or 3 days posttreatment with 5′ azacytidine.