The cenH3 histone variant defines centromeres in Giardia intestinalis

摘要: Histone H3 variants play critical roles in the functional specialization of chromatin by epigenetically marking centromeric and transcriptionally active or silent genes. Specifically, cenH3 histone variant acts as primary epigenetic determinant site kinetochore assembly at centromeres. Although function is well studied plants, animals, fungi, there little knowledge evolutionary conservation their most protists. We find that Giardia intestinalis--a diplomonad parasite with two equivalent nuclei--has phylogenetically distinct N-terminal extensions nonconserved promoters. To determine role dynamics, conventional were GFP-tagged, subcellular location was monitored during interphase mitosis. demonstrate one cenH3-like has a conserved The other (H3B) punctate distribution on chromosomes, but does not colocalize transcriptional regions indicated H3K4 methylation. suggest H3B could instead mark noncentromeric heterochromatin. member Diplomonads represents an ancient divergence from metazoans fungi. confirm modulating architecture, monocentric chromosomes represent ancestral chromosome morphology.