The meiosis-specific modification of mammalian telomeres

Abstract

During meiosis, rapid chromosome movements within the nucleus enable homologous chromosomes to acquire physical juxtaposition. In most organisms, chromosome ends, telomeres, tethered to the transmembrane LINC-complex mediate this movement by transmitting cytoskeletal forces to the chromosomes. While the majority of molecular studies have been performed using lower eukaryotes as model systems, recent studies have identified mammalian meiotic telomere regulators, including the LINC-complex SUN1/KASH5 and the meiosis-specific telomere binding protein TERB1. This review highlights the molecular regulations of mammalian meiotic telomeres in comparison with other model systems and discusses some future perspectives.

Keywords: chromosome; cohesin; meiosis; nuclear envelope; telomere.

Figure 1. The conserved rapid chromosome movement during meiotic prophase I. During meiosis, telomeres (or pairing center in worm) are tethered to the NE and assemble the transmembrane LINC complex to the association sites. LINC complex, associating with cytoskeletal motors, facilitates the rapid chromosome movements along the NE (leptotene to zygotene), accompanying transient bouquet configuration of meiotic chromosomes (bouquet). Then, chromosome acquires the homolog association (pachytene).

Figure 2. Modification of mammalian meiotic telomeres by TERB1. (A) Domain conformations of TRF1 and TERB1. TRF1 is composed of an N-terminus TRF homology domain, required both for TRF1 homodimerization and TERB1 hetero‐binding, and C-terminus MYB domain, required for telomere DNA binding. TERB1 is composed of N-terminus extension, which binds to SUN1’s N terminus, C-terminus TRFB domain, required for TRF1 binding and TERB1 telomere localization in vivo, and MYB domain. SA3 binding is mediated by TERB1 C terminus. In particular, the very C-terminal MYB domain (thick line) is essential for cohesin telomere accumulation in vivo. (B) Models and future perspectives (highlighted in red word) of telomere regulations during mammalian meiosis.