Expression of the meiosis-specific synaptonemal complex protein 1 in a heterologous system results in the formation of large protein structures.

The synaptonemal complex is a meiosis-specific structure essential for synapsis of homologous chromosomes. The synaptonemal complex protein 1 (SCP1) is a major constituent of the transversal filament, a fibrous structure that connects the central element of the synaptonemal complex with the two lateral elements. The SCP1 protein forms filamentous dimers with the two molecules that have the same polarity, with the C-termini being anchored in the lateral elements and the N-termini reaching into the central element. We investigated whether the SCP1 protein can take part in the formation of higher order protein structures by expressing it in a heterologous system. We find that expression of SCP1 in Swiss-3T3 fibroblast cells results in the formation of large protein structures. These protein structures resemble a higher order protein structure produced by overexpression of a yeast transversal filament protein in meiotic cells. Our results show that SCP1 is a structural protein and that it most likely is directly involved in the assembly of the synaptonemal complex.