角蛋白纤维的新功能──在爪蟾卵提取物核膜重组装中的作用

THE NOVEL ROLE OF KERATIN FILAMENTS IN NUCLEAR ENVELOPE REASSEMBLY IN XENOPUS EGG EXTRACTS

激活的非洲爪蟾（Xenopuslaevis）卵提取物温育过程中，直径200nm的膜泡附着在一种直径10nm纤维上，形成“珠链”结构。用透射电镜整装制样技术观察了温育中“珠链”结构的形成过程，发现10nm纤维可抗Triton抽提，免疫荧光和蛋白免疫印迹试验表明10nm纤维可能是由56kD的碱性角蛋白与42kD的酸性角蛋白构成。向提取物中加入碱性用蛋白抗体AE3则可抑制环形片层的形成，而核膜的组装也受到很大影响。这些结果显示角蛋白纤维在核股重新形成的过程中起到重要的作用。

We report here a new 'strings-of-pearls' structure, in which 200nm membrane vesicles attached to 10nm filaments, formed in activated Xenopus egg extracts after incubation, observed by high resolution low voltage SEM or TEM whole-mount preparations. These vesicles fused together along the filaments to form annulate lamellae (AL),or attached to demembraned sperm chromatin to initiate assembly of NE. Immunoblotting and immunofluorescent assay with anti-keratin antibodies (AE3, AEl and C-2562)showed that the 10nm filaments were constituted mainly of 40kD acidic keratin and 56kD basic keratin. Addition of AE3 to the extracts resulted in the inhibition of AL formation and defective assembly of NE. These results suggest that keratin filaments may play an important role in nuclear assembly in Xenopus egg extracts which is not reported before.