Repurposing of Synaptonemal Complex Proteins for Kinetochores in Kinetoplastida

Abstract

Chromosome segregation in eukaryotes is driven by a macromolecular protein complex called the kinetochore that connects centromeric DNA to microtubules of the spindle apparatus. Kinetochores in well-studied model eukaryotes consist of a core set of proteins that are broadly conserved among distant eukaryotic phyla. In contrast, unicellular flagellates of the class Kinetoplastida have a unique set of kinetochore components. The evolutionary origin and history of these kinetochores remains unknown. Here, we report evidence of homology between three kinetoplastid kinetochore proteins KKT16-18 and axial element components of the synaptonemal complex, such as the SYCP2:SYCP3 multimers found in vertebrates. The synaptonemal complex is a zipper-like structure that assembles between homologous chromosomes during meiosis to promote recombination. Using a sensitive homology detection protocol, we identify divergent orthologues of SYCP2:SYCP3 in most eukaryotic supergroups including other experimentally established axial element components, such as Red1 and Rec10 in budding and fission yeast, and the ASY3:ASY4 multimers in land plants. These searches also identify KKT16-18 as part of this rapidly evolving protein family. The widespread presence of the SYCP2-3 gene family in extant eukaryotes suggests that the synaptonemal complex was likely present in the last eukaryotic common ancestor. We found at least twelve independent duplications of the SYCP2-3 gene family throughout the eukaryotic tree of life, providing opportunities for new functional complexes to arise, including KKT16-18 in Trypanosoma brucei. We propose that kinetoplastids evolved their unique kinetochore system by repurposing meiotic components of the chromosome synapsis and homologous recombination machinery that were already present in early eukaryotes.

Studying meiosis in mitosis: Activating the meiosis-specific Red1-Hop1-Mek1 complex in mitotic budding yeast cells

“…The largest species we observed was determined at ∼209 kDa, which corresponds well to a 1:1 complex of Hop1 and Red1 I743R (theoretical molecular mass of 212 kDa). We observed no species that would correspond to a Red1 tetramer, and we assume this to be a concentration dependent effect, consistent with other components of the synaptonemal complex 4, 77 , to which the C-terminus of Red1 is functionally and evolutionarily related 73 . We also observed masses that correspond to both free Hop1 and free Red1 I743R -MBP (∼81 kDa and ∼140 kDa respectively; theoretical mass 71 kDa and 138 kDa, respectively).…”

“…These data suggest also that, in addition to its described interaction with Hop1 (via its CM, encoded in Red1 340-362 ; see also below 6, 18, 24 ), Red1 appears to encode a Mek1-interaction region. Red1 contains a conserved structured NH2-terminal domain (amino acids 1-340) – likely encoding an Armadillo repeat (ARML) domain and a Pleckstrin homology (PH) domain 61, 72, 73 ( Figure 2c , and see below). This module is followed by a CM sequence (Red1 340-362 ) that mediates interaction with Hop1 17, 24 .…”

“…a. Previously identified Red1 orthologs from different budding yeasts 73 were aligned using MUSCLE. A subset of these sequences were then used to generate a MSA that was mapped onto the surface of Red1 1-232 using ConSurf 102 .…”

Repurposing of synaptonemal complex proteins for kinetochores in Kinetoplastida

“…A detailed description/manual is available to replicate these analyses/visualizations (see §5 and electronic supplementary material, file S6 for description). The same electronic supplementary material files were also deposited in the FigShare repository at doi:10.6084/ m9.figshare.13725787 [110].…”

Oligopaint DNA FISH as a tool for investigating meiotic chromosome dynamics in the silkworm,Bombyx mori

“…Importantly, the recent sequencing of the B. mori genome revealed that there is a high degree of sequence homology between silkworm genes and mammalian disease genes (61,(74)(75)(76). Furthermore, Bombyx represents an excellent insect model system for studying meiosis, as SC constituents in non-Drosophilid arthropods are closely aligned with vertebrates, while Drosophila harbor a unique suite of SC factors (77,78). Finally, B. mori Here, we take advantage of the B. mori model system to visualize single chromosome dynamics in meiosis using the Oligopaints technology.…”