Assessment of ‘DNA-breaks’ in nuclei and gaps in kinetoplast circles.

(A) Percentage of cells positive for a TUNEL signal. ***, P < 0.001 from Students t-test. The microscopy images show an example of the kinetoplast-associated TUNEL signal in NT cells. (B) Example images of TUNEL signals, always associated with the kinetoplast (k) rather than the nucleus (n), at different cell cycle stages; G₁, S, G₂ and post M (post mitotic). Dashed boxes indicate magnified regions shown in C. (C) Percentage of cells in each cycle stage positive for TUNEL signals, inset images show magnified signals from B as indicated by dashed boxes. (D) Examples of TUNEL signals in none or all four kinetoplasts following suramin treatment. (E) Percentage of cells positive for γH2A signals. The microscopy images show an example of the nuclear γH2A signal in NT cells. MMS, methyl methanesulfonate. Other details in A, C and E as in Fig 2A; error bars, SD; N = 2; all scale bars, 5 μm.