Trypanosoma brucei brucei: differences in the nuclear chromatin of bloodstream forms and procyclic culture forms

Abstract

SUMMARYNucleosome filaments of two stages of the life-cycle of Trypanosoma brucei brucei, namely bloodstream forms and procyclic culture forms, were investigated by electron microscopy. Chromatin of bloodstream forms showed a salt-dependent condensation. The level of condensation was higher than that shown by chromatin from procyclic culture forms, but 30 nm fibres as formed in rat liver chromatin preparations were not found. Analysis of histones provided new evidence for the existence of HI-like proteins, which comigrated in the region of the core histones in SDS-PAGE and in front of the core histones in Triton acid urea gels. Differences were found between the HI-like proteins of the two trypanosome stages as well as between the core histones in their amount, number of bands and banding pattern. It can be concluded that T. b. brucei contains a full set of histones, including HI-like proteins, and that the poor condensation of its chromatin is not due to the absence of H1, but most probably due to histone-DNA interaction being weak. It is obvious that structural and functional differences of the chromatin exist not only between T. b. brucei and higher eukaryotes, but also between various stages of the life-cycle of the parasite. It is therefore not adequate to investigate the chromatin only of the procyclic culture forms as a model for all stages of the life-cycle of T. b. brucei.

Nucleus-Encoded Histone H1-Like Proteins Are Associated with Kinetoplast DNA in the Trypanosomatid Crithidia fasciculata

“…The similarity of the kinetoplast-associated proteins described here to the H1 histones raises a note of caution regarding earlier claims of H1 histones in trypanosomatids (5,8,22). In the absence of evidence for the presence of these proteins in the nucleus, the possible kinetoplast origin of such proteins cannot be excluded.…”

Cell death in Leishmania induced by stress and differentiation: programmed cell death or necrosis?

“…69 Briefly, following lysis of the cells in a cavitation chamber (under 23 bars of nitrogen), the pellet was washed, resuspended in the nuclei storage solution and stored at 7708C. Nuclei were incubated at 308C with or without 5 mU of MNase per mg of DNA (based on OD at 260 nm) in pH 7.4 nuclei storage buffer (340 mM sacharose, 0.1 mM EDTA, 60 mM KCl, 15 mM NaCl, 0.15 mM spermin, 0.15 mM spermidin, 15 mM Tris) supplemented with 1 mM CaCl 2 .…”

“…Nuclei were incubated at 308C with or without 5 mU of MNase per mg of DNA (based on OD at 260 nm) in pH 7.4 nuclei storage buffer (340 mM sacharose, 0.1 mM EDTA, 60 mM KCl, 15 mM NaCl, 0.15 mM spermin, 0.15 mM spermidin, 15 mM Tris) supplemented with 1 mM CaCl 2 . 69 Digestion was blocked by the addition of 2.5 mM EDTA. DNA was extracted with phenol/chloroform and precipitated before loading on a 2% agarose gel.…”

New Insights into the Molecular Mechanisms of Mitosis and Cytokinesis in Trypanosomes

“…In the bloodstream form, however, the kinetoplast replicates and segregates in the posterior portion of the cell, and both daughter kinetoplasts remain in the posterior region throughout the cell cycle, thus resulting in the KKNN configuration of cells before cytokinesis. In addition to the morphological difference between the life cycle forms, life cycle-specific differences in many other cellular processes, including chromatin structure (Schlimme et al, 1993), glucose transport (Munoz-Antonia et al, 1991), maintenance of plasma membrane potential (Van der Heyden and Docampo, 2002), cell motility (Broadhead et al, 2006), and cell cycle regulation (Hammarton et al, 2003; Li and Wang, 2006; Tu and Wang, 2004) have also been discovered. Nevertheless, the molecular mechanisms underlying these distinctions between the two life cycle forms remain poorly understood.…”