Molecular and Cellular Biology, August 2001, p. 5667-5677, Vol. 21, No. 16
0270-7306/01/$04.00+0 DOI: 10.1128/MCB.21.16.5667-5677.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Department of Cell and Molecular Biology and Center for Genomics Research, Karolinska Institutet, S-171 77 Stockholm, Sweden1; Department of Biology, York University, Toronto, Ontario M3J 1P3, Canada2; Laboratorie de Neurobiologie Cellulaire, UMR CNRS/UNSA 6549, Faculté de Médecine, 06107 Nice cedex 2, France3; Institute for Gene Therapy and Molecular Medicine, Mount Sinai School of Medicine, New York, New York 10029-65744; Department of Immunology and Oncology, Centro Nacional de Biotecnologia, UAM Campus Cantoblanco, Madrid E-28049, Spain5; and Laboratory of Genetics, Wageningen University, NL-6703HA Wageningen, The Netherlands6
Received 8 March 2001/Returned for modification 27 April 2001/Accepted 7 May 2001
The behavior of meiotic chromosomes differs in several respects from that of their mitotic counterparts, resulting in the generation of genetically distinct haploid cells. This has been attributed in part to a meiosis-specific chromatin-associated protein structure, the synaptonemal complex. This complex consist of two parallel axial elements, each one associated with a pair of sister chromatids, and a transverse filament located between the synapsed homologous chromosomes. Recently, a different protein structure, the cohesin complex, was shown to be associated with meiotic chromosomes and to be required for chromosome segregation. To explore the functions of the two different protein structures, the synaptonemal complex and the cohesin complex, in mammalian male meiotic cells, we have analyzed how absence of the axial element affects early meiotic chromosome behavior. We find that the synaptonemal complex protein 3 (SCP3) is a main determinant of axial-element assembly and is required for attachment of this structure to meiotic chromosomes, whereas SCP2 helps shape the in vivo structure of the axial element. We also show that formation of a cohesin-containing chromosomal core in meiotic nuclei does not require SCP3 or SCP2. Our results also suggest that the cohesin core recruits recombination proteins and promotes synapsis between homologous chromosomes in the absence of an axial element. A model for early meiotic chromosome pairing and synapsis is proposed.
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