Golubovskaya Inna N, Hamant Olivier, Timofejeva Ljuda, Wang Chung-Ju Rachel, Braun David, Meeley Robert, Cande W Zacheus
Department of Molecular and Cell Biology, University California, Berkeley, CA 94720, USA.
J Cell Sci. 2006 Aug 15;119(Pt 16):3306-15. doi: 10.1242/jcs.03054. Epub 2006 Jul 25.
REC8 is a master regulator of chromatin structure and function during meiosis. Here, we dissected the functions of absence of first division (afd1), a maize rec8/alpha-kleisin homolog, using a unique afd1 allelic series. The first observable defect in afd1 mutants is the inability to make a leptotene chromosome. AFD1 protein is required for elongation of axial elements but not for their initial recruitment, thus showing that AFD1 acts downstream of ASY1/HOP1. AFD1 is associated with the axial and later the lateral elements of the synaptonemal complex. Rescuing 50% of axial element elongation in the weakest afd1 allele restored bouquet formation demonstrating that extent of telomere clustering depends on axial element elongation. However, rescuing bouquet formation was not sufficient for either proper RAD51 distribution or homologous pairing. It provides the basis for a model in which AFD1/REC8 controls homologous pairing through its role in axial element elongation and the subsequent distribution of the recombination machinery independent of bouquet formation.
REC8是减数分裂过程中染色质结构和功能的主要调节因子。在此，我们利用独特的afd1等位基因系列剖析了玉米rec8/α- kleisin同源物——首次分裂缺失（afd1）的功能。afd1突变体中第一个可观察到的缺陷是无法形成细线期染色体。AFD1蛋白是轴向元件伸长所必需的，但不是其初始募集所必需的，因此表明AFD1在ASY1/HOP1下游起作用。AFD1与联会复合体的轴向元件相关，随后与横向元件相关。在最弱的afd1等位基因中挽救50%的轴向元件伸长恢复了花束形成，表明端粒聚集程度取决于轴向元件伸长。然而，挽救花束形成对于正确的RAD51分布或同源配对都不够。它为一个模型提供了基础，在该模型中，AFD1/REC8通过其在轴向元件伸长中的作用以及随后独立于花束形成的重组机制的分布来控制同源配对。
