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bioRxiv · 10.1101/2020.12.30.424799

Structural basis of meiotic chromosome synaptic elongation through hierarchical fibrous assembly of SYCE2-TEX12

Dunce, J. M.·Salmon, L. J.·Davies, O. R.
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Abstract

The synaptonemal complex (SC) is a supramolecular protein assembly that mediates synapsis between homologous chromosomes during meiosis. SC elongation along the chromosome length (up to 24 m) depends on its midline -fibrous component SYCE2-TEX12. Here, we report X-ray crystal structures of SYCE2-TEX12 as an individual building-block and upon assembly within a fibrous lattice. We combine these structures with mutagenesis, biophysics and electron microscopy to reveal the hierarchical mechanism of SYCE2-TEX12 fibre assembly. SYCE2-TEX12s building-blocks are 2:2 coiled-coils which dimerise into 4:4 hetero-oligomers and interact end-to-end and laterally to form 10-nm fibres, which intertwine within 40-nm bundled micrometre-long fibres that define the SCs midline structure. This assembly mechanism bears striking resemblance with intermediate filament proteins vimentin, lamin and keratin. Thus, SYCE2-TEX12 exhibits behaviour typical of cytoskeletal proteins to provide an -fibrous SC backbone that structurally underpins synaptic elongation along meiotic chromosomes.

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Dunce, J. M., Salmon, L. J., Davies, O. R.. 2020-12-31. Structural basis of meiotic chromosome synaptic elongation through hierarchical fibrous assembly of SYCE2-TEX12. https://doi.org/10.1101/2020.12.30.424799

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