Scherf U, Pastan I, Willingham M C, Brinkmann U
Laboratory of Molecular Biology, Division of Basic Sciences, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-4255, USA.
Proc Natl Acad Sci U S A. 1996 Apr 2;93(7):2670-4. doi: 10.1073/pnas.93.7.2670.
Human CAS cDNA contains a 971-aa open reading frame that is homologous to the essential yeast gene CSE1. CSE1 is involved in chromosome segregation and is necessary for B-type cyclin degradation in mitosis. Using antibodies to CAS, it was shown that CAS levels are high in proliferating and low in nonproliferating cells. Here we describe the distribution of CAS in cells and tissues analyzed with antibodies against CAS. CAS is an approximately 100-kDa protein present in the cytoplasm of proliferating cells at levels between 2 x 10(5) and 1 x 10(6) molecules per cell. The intracellular distribution of CAS resembles that of tubulin. In interphase cells, anti-CAS antibody shows microtubule-like patterns and in mitotic cells it labels the mitotic spindle. CAS is removed from microtubules by mild detergent treatment (cytoskeleton preparations) and in vincristine- or taxol-treated cells. CAS is diffusely distributed in the cytoplasm with only traces present in tubulin paracrystals or bundles. Thus, CAS appears to be associated with but not to be an integral part of microtubules. Immunohistochemical staining of frozen tissues shows elevated amounts of CAS in proliferating cells such as testicular spermatogonia and cells in the basal layer cells of the colon. CAS was also concentrated in the respiratory epithelium of the trachea and in axons and Purkinje cells in the cerebellum. These cells contain many microtubules. The cellular location of CAS is consistent with an important role in cell division as well as in ciliary movement and vesicular transport.
人CAS cDNA含有一个971个氨基酸的开放阅读框，与酵母必需基因CSE1同源。CSE1参与染色体分离，是有丝分裂中B型细胞周期蛋白降解所必需的。使用抗CAS抗体表明，CAS水平在增殖细胞中高，在非增殖细胞中低。在此我们描述了用抗CAS抗体分析的CAS在细胞和组织中的分布。CAS是一种约100 kDa的蛋白质，存在于增殖细胞的细胞质中，每个细胞中的水平在2×10⁵至1×10⁶个分子之间。CAS的细胞内分布类似于微管蛋白。在间期细胞中，抗CAS抗体显示出微管样模式，在有丝分裂细胞中它标记有丝分裂纺锤体。通过温和的去污剂处理（细胞骨架制备）以及在长春新碱或紫杉醇处理的细胞中，CAS从微管上被去除。CAS在细胞质中呈弥散分布，仅在微管蛋白副晶体或束中存在微量。因此，CAS似乎与微管相关，但不是微管的组成部分。冷冻组织的免疫组织化学染色显示，在增殖细胞如睾丸精原细胞和结肠基底层细胞中，CAS含量升高。CAS也集中在气管的呼吸上皮以及小脑中的轴突和浦肯野细胞中。这些细胞含有许多微管。CAS的细胞定位与它在细胞分裂以及纤毛运动和囊泡运输中的重要作用一致。
