During homolog recognition and pairing in meiosis, pairing centers at or near one end of each meiotic chromosome are localized to the nuclear envelope. SUN-1 is an evolutionarily conserved protein located in the inner nuclear membrane that appears to be directly involved in mediating telomere attachment in mice and yeast; in worms, a direct interaction between pairing center proteins and SUN-1 at the nuclear envelope has not yet been proved (1, 2). In sun-1
null mutants, none of the meiotic chromosomes are paired but the pairing centers are localized to the nuclear envelope (2). HIM-8 is a C2H2 zinc finger protein that binds specifically to the pairing center on the X chromosome and is necessary for the pairing of the X chromosome and for synapsis (3). When a zinc finger is mutated in him-8
, such as in e1489
or the tm611
deletion, the protein does not bind to the X pairing center, the X chromosomes do not pair, but the chromosomes are still located at the nuclear envelope. Thus, pairing and nuclear envelope attachment may be separable activities for the pairing center proteins. The autosomes are paired normally in him-8
mutants. The three ZIM proteins, which are highly related to HIM-8 in sequence, mediate pairing of the autosomes (4). We find that SUN-1 and HIM-8 physically associate with each other in a yeast two-hybrid assay. Preliminary evidence suggests a similar physical interaction occurs between SUN-1 and at least one of the ZIM proteins. This suggests a model whereby meiotic chromosomes are tethered to the nuclear envelope for pairing via a direct interaction between SUN-1 in the inner membrane and HIM-8 or one of the ZIM proteins on each specific chromosome. 1.Penkner et al. 2007. Develop. Cell 12: 873-885 2.Fridkin, et al., 2009. Cell Mol. Life Sci. 66: (in press) 3.Phillips et al. 2005 Cell 123: 1051-1063 4.Phillips and Dernburg 2006 Develop. Cell 11: 817-829.