Fig. 4. Effect of TbSIR2RP1 RNAi on cell sensitivity to DNA damage. (A) Northern blot analysis of mRNA levels from cells incubated for 24 h without (–) or with (+) tetracycline. rRNAs stained with ethidium bromide are shown as loading controls. (B) A similar northern blot was hybridized with probes corresponding to the entire ORF of two other trypanosomal homologues of SIR2 (TbSIR2RP2, accession No. AC119406; TbSIR2RP3, accession No. AF102869). (C) Western blot analysis of whole-cell lysate (1 × 10⁶ cell equivalents/lane) from uninduced (day 0) and tetracycline- induced cells (days 1–6) using anti-TbSIR2RP1 and anti-α-tubulin antibodies. (D) Cell survival curves are shown for uninduced (TET–) and tetracycline-induced cells (TET+) treated with different concentrations of MMS.