CHARACTERIZATION OF THE HISTONES OF TRYPANOSOMA-BRUCEI-BRUCEI BLOOD-STREAM FORMS

Five groups of histones were shown in Trypanosoma brucei biucei, displ aying qualitative and quantitative differences between two stages of t he parasite's life-cycle. The influence of the histones of T. b. bruce i bloodstream forms on the compaction pattern of the chromatin was inv estigated and their extractability in diluted acids and their amino ac id composition were analysed. While nonhistone proteins barely influen ced the formation of higher-order chromatin structures, the histone H1 -like proteins were essential for the regular spacing of the nucleosom es and the salt-dependent condensation of the nucleosome filament. Dif ferences were seen in the amino-acid composition of histones of bloods tream forms as compared to procyclic culture forms and higher eukaryot es which may explain the disparities seen in the condensation of the c hromatin between the two stages of the life cycle as well as the lack of a salt-dependent condensation into a 30 nm fiber. They point to an alternative method of organizing and processing the genetic informatio n in the nucleus of the trypanosome as compared to higher eukaryotes, the possible hosts of the parasite.