Kobe Advanced ICT Research Center, National Institute of Information and Communications Technology, Nishi-ku, Kobe 651-2492, Japan.
J Cell Biol. 2009 Nov 2;187(3):413-27. doi: 10.1083/jcb.200902122.
In many organisms, telomeres cluster to form a bouquet arrangement of chromosomes during meiotic prophase. Previously, we reported that two meiotic proteins, Bqt1 and -2, are required for tethering telomeres to the spindle pole body (SPB) during meiotic prophase in fission yeast. This study has further identified two novel, ubiquitously expressed inner nuclear membrane (INM) proteins, Bqt3 and -4, which are required for bouquet formation. We found that in the absence of Bqt4, telomeres failed to associate with the nuclear membranes in vegetative cells and consequently failed to cluster to the SPB in meiotic prophase. In the absence of Bqt3, Bqt4 protein was degraded during meiosis, leading to a phenotype similar to that of the bqt4-null mutant. Collectively, these results show that Bqt4 anchors telomeres to the INM and that Bqt3 protects Bqt4 from protein degradation. Interestingly, the functional integrity of telomeres is maintained even when they are separated from the nuclear envelope in vegetative cells.
在许多生物中，端粒在减数分裂前期聚集形成染色体的花束排列。之前，我们报道了两个减数分裂蛋白，Bqt1 和 -2，在有丝分裂前期将端粒与纺锤体极体（SPB）连接在一起是必需的。本研究进一步鉴定了两种新型的、普遍表达的核内膜（INM）蛋白，Bqt3 和 -4，它们是花束形成所必需的。我们发现，在 bqt4 缺失的情况下，端粒在营养细胞中无法与核膜结合，因此在减数分裂前期无法聚集到 SPB。在 bqt3 缺失的情况下，Bqt4 蛋白在减数分裂过程中被降解，导致与 bqt4 缺失突变体相似的表型。总之，这些结果表明 Bqt4 将端粒锚定在 INM 上，而 Bqt3 保护 Bqt4 免受蛋白降解。有趣的是，即使在营养细胞中端粒与核膜分离，端粒的功能完整性仍能得到维持。
