Figure 2.

Nuclear ultrastructure and chromatin state are affected by TcHMGB protein levels. (A) Transmission Electron Microscopy (TEM) analysis of the ultrastructure of the T. cruzi Dm28c/pTcINDEX-GW-TcHMGB(HA)₂ epimastigotes in the absence (Tet−, Panels A–C) or presence (Tet+, Panels D–F) of tetracycline. Note the augmented space occupied by euchromatin (eu) and the reduction of the nucleolus in induced (Tet+) (E,F) in relation to non-induced parasites (Tet−) (B,C). Arrows indicate the nucleolus and in panel C its distinct domains. Kinetoplast (k), flagellum (f), Golgi complex (gc) and the different nucleolus regions are also indicated. (B) Analysis of chromatin isolated from T. cruzi Dm28c/pTcINDEX-GW-TcHMGB(HA)₂ epimastigotes non-induced (−, lanes 1, 3, 5) or induced (+, lanes 2, 4, 6) with tetracycline (Tet). Chromatin from an equal number of cells was isolated and digested with 1 unit of micrococcal nuclease (MNase) for 0 (lanes 1, 2), 5 (lanes 3, 4) and 25 minutes (lanes 5, 6). Equal amounts of DNA were loaded on an ethidium bromide-stained 1% agarose gel. Note that in Tet−induced parasites, the characteristic ladder pattern is observed at shorter times compared to non-induced (Tet−). A representative experiment is shown, digestion products corresponding to DNA that has been bound to mono- di- and tri-nucleosomes are indicated. The corresponding full-length gel is presented in Supplementary Fig. S4.