García Ignacio, Jiménez David, Martín Victoria, Durán Angel, Sánchez Yolanda
Instituto de Microbiología Bioquímica, CSIC/Universidad de Salamanca and Departamento de Microbiología y Genética, Universidad de Salamanca, Edificio Departamental, 37007 Salamanca, Spain.
Biol Cell. 2005 Jul;97(7):569-76. doi: 10.1042/BC20040096.
In animal cells, cytokinesis occurs by constriction of an actomyosin ring. In fission yeast, ring constriction is followed by deposition of a multilayered division septum that must be cleaved to release the two daughter cells. Although many studies have focused on the actomyosin ring and septum assembly, little is known about the later steps involving the cleavage of the cell wall.
We identified a novel gene in Schizosaccharomyces pombe, namely the agn1(+) gene that has homology to fungal 1,3-alpha-glucanases (mutanases). Disruption of the agn1(+) gene is not lethal to the cells, but does interfere with their separation, whereas overexpression of Agn1p is toxic and causes cell lysis. Agn1p levels reach a peak during septation and the protein localizes to the septum region before cell separation. Moreover, agn1(+) is responsible for the 1,3-alpha-glucanase activity, which shows a maximum at the end of septation.
Our results clearly suggest the existence of a relationship between agn1(+), 1,3-alpha-glucanase activity and the completion of septation in S. pombe. Agn1p could be involved in the cleavage of the cylinder of the old wall that surrounds the primary septum, a region rich in alpha-glucans.
在动物细胞中，胞质分裂通过肌动球蛋白环的收缩发生。在裂殖酵母中，环收缩之后是多层分裂隔膜的沉积，必须将其裂解才能释放出两个子细胞。尽管许多研究聚焦于肌动球蛋白环和隔膜组装，但对于涉及细胞壁裂解的后续步骤却知之甚少。
我们在粟酒裂殖酵母中鉴定出一个新基因，即agn1(+)基因，它与真菌1,3-α-葡聚糖酶（变聚糖酶）具有同源性。agn1(+)基因的破坏对细胞并非致命，但确实会干扰它们的分离，而Agn1p的过表达具有毒性并导致细胞裂解。Agn1p水平在隔膜形成期间达到峰值，并且该蛋白在细胞分离之前定位于隔膜区域。此外，agn1(+)负责1,3-α-葡聚糖酶活性，该活性在隔膜形成结束时达到最大值。
我们的结果清楚地表明粟酒裂殖酵母中agn1(+)、1,3-α-葡聚糖酶活性与隔膜形成的完成之间存在关联。Agn1p可能参与围绕初级隔膜的旧壁圆柱体的裂解，初级隔膜是富含α-葡聚糖的区域。
