Inner nuclear membrane protein Ima1 is dispensable for intranuclear positioning of centromeres
Inner nuclear membrane protein Ima1 is dispensable for intranuclear positioning of centromeres
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DOI：
10.1111/j.1365-2443.2011.01544.x
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发表时间：
2011-10-01
期刊：
影响因子：
2.1
通讯作者：
Haraguchi, Tokuko
中科院分区：
文献类型：
--
作者：
Hiraoka, Yasushi;Maekawa, Hiromi;Haraguchi, Tokuko
核内膜(INM)蛋白在核内染色体的空间组织中发挥作用。在裂殖酵母中，SAD1是一种保守的太阳结构域家族的INM蛋白，在减数分裂前期发挥着沿着核膜移动染色体的积极作用。Ima1是最近发现的另一个保守的INM蛋白。先前的一项研究声称，Ima1对有丝分裂细胞的生长是必不可少的，它将着丝粒异染色质连接到纺锤体-极体。然而，我们得到的结果与先前提出的Ima1的作用相矛盾：Ima1对于有丝分裂细胞的生长或着丝粒定位是必不可少的。这一差异归因于先前研究中使用的不正确的ima1缺失突变体。我们的结果表明，Ima1与LEM结构域家族的另外两个保守的INM蛋白合作，这两个蛋白与人类的Man1和Lem2同源。三种INM蛋白中的任何一种的缺失对有丝分裂细胞的生长没有影响；然而，所有这些蛋白质的缺失都会导致有丝分裂细胞的生长和核膜形态的严重缺陷。考虑到这三个INM蛋白都与SAD1相互作用，这些结果表明Ima1、Lem2和Man1至少在核膜组织中扮演着部分多余的角色。
Inner nuclear membrane (INM) proteins play a role in spatial organization of chromosomes within the nucleus. In the fission yeast Schizosaccharomyces pombe, Sad1, an INM protein of the conserved SUN-domain family, plays an active role in moving chromosomes along the nuclear membranes during meiotic prophase. Ima1 is another conserved INM protein recently identified. A previous study claimed that Ima1 is essential for mitotic cell growth, linking centromeric heterochromatin to the spindle-pole body. However, we obtained results contradictory to the previously proposed role for Ima1: Ima1 was dispensable for mitotic cell growth or centromere positioning. This discrepancy was attributed to incorrect ima1 deletion mutants used in the previous study. Our results show that Ima1 collaborates with two other conserved INM proteins of the LEM-domain family that are homologous to human Man1 and Lem2. Loss of any one of three INM proteins has no effect on mitotic cell growth; however, loss of all these proteins causes severe defects in mitotic cell growth and nuclear membrane morphology. Considering that all three INM proteins interact with Sad1, these results suggest that Ima1, Lem2 and Man1 play at least partially redundant roles for nuclear membrane organization.