Steels Jonathan D, Estey Mathew P, Froese Carol D, Reynaud Dénis, Pace-Asciak Cecil, Trimble William S
Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada.
Cell Motil Cytoskeleton. 2007 Oct;64(10):794-807. doi: 10.1002/cm.20224.
Since their essential role in cytokinesis was first shown in yeast, the septins have been described to function in diverse cellular contexts. The members of this unique class of GTPases are capable of binding and hydrolyzing GTP, associating with membranes and oligomerizing into higher order structures. Here we describe Sept12, a novel septin, identified in a yeast two hybrid screen using Sept5 as the bait. Sept12 contains the primary sequence elements of a septin and is capable of interacting with other septins. In addition, Sept12 purifies with bound nucleotide and binds to phosphoinositides, confirming its identity as a septin. RT-PCR and Northern blots reveal that Sept12 mRNA is expressed predominantly in testis, and this is supported by tissue Western blots. In rats, Sept12 protein levels rise upon sexual maturity and the Sept12 protein colocalizes with the annulus in isolated mature spermatozoa. Further, coexpression of Sept12 with Sept4, an essential annulus component, results in complete colocalization of both proteins into robust and highly curved filaments in CHO cells. This study suggests Sept12 may be involved in mammalian fertility.
自从在酵母中首次发现其在胞质分裂中发挥重要作用以来，人们已发现septin蛋白家族在多种细胞环境中发挥作用。这类独特的GTP酶成员能够结合并水解GTP，与膜结合并寡聚形成更高阶的结构。在此，我们描述了Sept12，这是一种新型的septin蛋白，在以Sept5为诱饵的酵母双杂交筛选中被鉴定出来。Sept12包含septin蛋白的主要序列元件，并且能够与其他septin蛋白相互作用。此外，Sept12能与结合的核苷酸一起纯化，并与磷酸肌醇结合，证实了它作为septin蛋白的身份。逆转录聚合酶链反应（RT-PCR）和Northern印迹显示，Sept12 mRNA主要在睾丸中表达，组织蛋白质印迹也证实了这一点。在大鼠中，Sept12蛋白水平在性成熟时升高，并且Sept12蛋白在分离出的成熟精子中与环带共定位。此外，Sept12与环带的一个重要组成部分Sept4共表达时，会导致这两种蛋白在CHO细胞中完全共定位形成粗壮且高度弯曲的细丝。这项研究表明Sept12可能参与哺乳动物的生育过程。
