Amsterdam A, Pitzer F, Baumeister W
Department of Hormone Research, Weizmann Institute of Science, Rehovot, Israel.
Proc Natl Acad Sci U S A. 1993 Jan 1;90(1):99-103. doi: 10.1073/pnas.90.1.99.
We describe the isolation and characterization of proteasomes from recently established immortalized ovarian granulosa cell lines and their intracellular distribution during mitosis and during cAMP-induced differentiation, as revealed by immunofluorescence microscopy. In interphase, proteasomes were localized in small clusters throughout the cytoplasm and the nuclear matrix. In prophase, a substantial increase in proteasomal staining was observed in the perichromosomal area. A dramatic increase occurred in metaphase and in early anaphase; the chromosomes remained unstained. In late anaphase, intensive staining remained associated mainly with the spindle fibers. In telophase and early interphase of the daughter cells, intensive staining of proteasomes persisted in the nuclei. In contrast, in cells stimulated to differentiate by forskolin, which substantially elevates intracellular cAMP in these cell lines, only a weak staining of proteasomes was revealed in both the nucleus and the cytoplasm. Double staining of nondividing cells with antibodies to proteasomes and to tubulin did not show colocalization of proteasomes and microtubules. In contrast, dividing cells show a preferential concentration of proteasomes around spindle microtubules during metaphase and anaphase. The observed spatial and temporal distribution pattern of proteasomes during mitosis is highly reminiscent of the behavior of cyclins [Pines, J. & Hunter, T. (1991) J. Cell Biol. 115, 1-17]. Since proteasome accumulation appears to coincide with disappearance of cyclins A and B1 from the spindle apparatus, it is suggested that proteasomes may play a role in termination of mitosis by degrading the cyclins, which act as regulatory elements.
我们描述了从最近建立的永生化卵巢颗粒细胞系中分离和鉴定蛋白酶体，以及通过免疫荧光显微镜观察到的它们在有丝分裂期间和cAMP诱导分化过程中的细胞内分布。在间期，蛋白酶体定位在整个细胞质和核基质的小簇中。在前期，在染色体周围区域观察到蛋白酶体染色显著增加。在中期和早后期发生了急剧增加；染色体仍未染色。在晚后期，强烈染色主要仍与纺锤体纤维相关。在子细胞的末期和早间期，蛋白酶体在细胞核中持续强烈染色。相反，在用福斯可林刺激分化的细胞中，福斯可林可显著提高这些细胞系中的细胞内cAMP水平，在细胞核和细胞质中仅发现蛋白酶体的微弱染色。用蛋白酶体抗体和微管蛋白抗体对非分裂细胞进行双重染色，未显示蛋白酶体与微管共定位。相反，分裂细胞在中期和后期显示蛋白酶体优先集中在纺锤体微管周围。在有丝分裂期间观察到的蛋白酶体的时空分布模式与细胞周期蛋白的行为高度相似[派因斯，J. & 亨特，T.（1991年）《细胞生物学杂志》115卷，1 - 17页]。由于蛋白酶体的积累似乎与细胞周期蛋白A和B1从纺锤体装置中消失同时发生，有人提出蛋白酶体可能通过降解作为调节元件的细胞周期蛋白在有丝分裂的终止中发挥作用。
