The synaptonemal complex protein SCP3 can form multistranded, cross-striated fibers in vivo.
The synaptonemal complex protein SCP3 is part of the lateral element of the synaptonemal complex, a meiosis-specific protein structure essential for synapsis of homologous chromosomes. We have investigated the fiber-forming properties of SCP3 to elucidate its role in the synaptonemal complex. By synthesis of SCP3 in cultured somatic cells, it has been shown that SCP3 can self-assemble into thick fibers and that this process requires the COOH-terminal coiled coil domain of SCP3, as well as the NH2-terminal nonhelical domain. We have further analyzed the thick SCP3 fibers by transmission electron microscopy and immunoelectron microscopy. We found that the fibers display a transversal striation with a periodicity of approximately 20 nm and consist of a large number of closely associated, thin fibers, 5-10 nm in diameter. These features suggest that the SCP3 fibers are structurally related to intermediate filaments. It is known that in some species the lateral elements of the synaptonemal complex show a highly ordered striated structure resembling that of the SCP3 fibers. We propose that SCP3 fibers constitute the core of the lateral elements of the synaptonemal complex and function as a molecular framework to which other proteins attach, regulating DNA binding to the chromatid axis, sister chromatid cohesion, synapsis, and recombination.
Yuan
L
L
Department of Cell and Molecular Biology (CMB), The Medical Nobel Institute, Karolinska Institutet, S-171 77 Stockholm, Sweden.
Pelttari
J
J
Brundell
E
E
Björkroth
B
B
Zhao
J
J
Liu
J G
JG
Brismar
H
H
Daneholt
B
B
Höög
C
C
D016475:3T3 Cells; D000818:Animals; D016466:CHO Cells; D018797:Cell Cycle Proteins; D002467:Cell Nucleus / Q000378:metabolism / Q000648:ultrastructure; D006224:Cricetinae; D003593:Cytoplasm / Q000378:metabolism / Q000648:ultrastructure; D004268:DNA-Binding Proteins; D007739:L Cells; D046911:Macromolecular Substances; D008540:Meiosis; D051379:Mice; D008854:Microscopy, Electron; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation; D051381:Rats; D013573:Synaptonemal Complex / Q000502:physiology*; D014162:Transfection
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D046911:Macromolecular Substances; D009687:Nuclear Proteins; C489754:Sycp1 protein, mouse; C078744:Sycp1 protein, rat; C490062:Sycp3 protein, mouse; C085453:Sycp3 protein, rat