AI Insight
Researchers have discovered how kinetoplastid parasites assemble their kinetochores at centromeres despite lacking the usual centromere-marking histone protein CENP-A. The study shows that the KKT2 protein's centromere localization domain recognizes and binds to the free N-terminus of histone H3, but this binding is completely prevented by even minimal methylation of the histone's N-terminal amino group. This suggests that kinetoplastids mark their centromeres negatively, by methylating histone H3 everywhere except at centromeres, rather than using a specialized histone variant like other eukaryotes.
Why it matters
This finding reveals a novel mechanism of centromere specification that differs fundamentally from the universal eukaryotic strategy, providing insights into chromosome segregation in disease-causing parasites like Trypanosoma brucei (which causes African sleeping sickness). Understanding these unique kinetochore assembly mechanisms could potentially inform the development of antiparasitic drugs that target cell division in these organisms.
Understand the Science
⚠️ Preprint – Noch nicht peer-reviewed
Dieser Artikel wurde noch nicht von unabhängigen Experten begutachtet. Die Ergebnisse sind vorläufig und sollten mit Vorsicht interpretiert werden.
Kinetochores are multiprotein complexes that drive chromosome segregation in eukaryotes. Kinetoplastids, a group of early-diverging eukaryotes that lack canonical kinetochore components, have a unique set of kinetochore proteins. How their kinetochores are assembled specifically at centromeres in the absence of a centromere-specific histone H3 variant CENP-A remains unknown. Here, we demonstrate that the centromere localization (CL) domain of KKT2 has similarities to a ZZ domain. An invariant aspartate present in histone H3-binding ZZ domains is conserved in the KKT2 CL domain. Using nuclear magnetic resonance (NMR) spectroscopy and isothermal titration calorimetry (ITC), we show that Trypanosoma brucei KKT2 CL binds the N-terminus of histone H3. Strikingly, even mono-methylation of the N-terminal amino group of histone H3 abolishes the binding. Our study raises a possibility that centromere-specific kinetochore assembly in T. brucei is ensured by abundant N-terminal methylations of histone H3 in non-centromeric regions.