Wenkert D, Allis C D
J Cell Biol. 1984 Jun;98(6):2107-17. doi: 10.1083/jcb.98.6.2107.
Vegetative cells of the ciliated protozoan Tetrahymena thermophila contain a transcriptionally active macronucleus and a transcriptionally inactive micronucleus. Earlier studies ( Allis , C. D., C. V. C. Glover , J. K. Bowen, and M. A. Gorovsky , 1980, Cell, 20:609-617; and Allis , C. D., Y. S. Ziegler , M. A. Gorovsky , and J. B. Olmsted, 1982, Cell, 31:131-136) demonstrated the existence of a macronuclear-specific histone variant, hv1 , which is enriched in small punctate regions in nucleoli of several mammalian cell lines. These observations suggest that this histone variant is highly conserved in evolution and may be associated with actively transcribed sequences. Despite large differences in structure and function during vegetative growth, macro- and micronuclei are related. During conjugation, the sexual phase of the life cycle in Tetrahymena, postzygotic division products of micronuclei give rise to new micro- and macronuclei, while the old macronucleus moves to the posterior of each cell and is eliminated. In this study using antiserum specific for hv1 , we determined by indirect immunofluorescence the time during conjugation at which hv1 first appears in the developing new macronuclei. In growing, starved, and young mating cells (2-5 h after mixing opposite mating types), only macronuclei are detected with affinity-purified antibodies against hv1 . Newly formed macronuclei are either not stained or only weakly stained in cells in which the old macronucleus is located in the center of the cell. However, new macronuclei are clearly observed in cells in which the old macronucleus has moved to the posterior of the cell (approximately 8 h). During later stages of conjugation (10-16 h), the intensity of hv1 staining in new macronuclei increases with time corresponding to the increasing DNA content of these nuclei. Disappearance of detectable hv1 from old macronuclei begins nearly 1 h after these nuclei reach the posterior cytoplasm (approximately 9-10 h) and is sometimes complete before these nuclei are eliminated from the cells. Autoradiography of cells labeled for brief periods with [3H]uridine shows that new macronuclei begin to synthesize RNA very soon after the second postzygotic division (approximately 8 h). During stages when hv1 is clearly detected in new macronuclei, anlagen are active in RNA synthesis. RNA synthesis in old macronuclei ceases very close to the time when RNA synthesis begins in new macronuclei. Thus, the addition of hv1 coincides closely with the transformation of a transcriptionally inactive germinal nucleus into that of a transcriptionally active somatic nucleus. We suspect that addition of hv1 plays a fundamental role in
纤毛原生动物嗜热四膜虫的营养细胞含有一个转录活跃的大核和一个转录不活跃的小核。早期研究（阿利斯，C.D.，C.V.C.格洛弗，J.K.鲍恩，和M.A.戈罗夫斯基，1980年，《细胞》，20:609 - 617；以及阿利斯，C.D.，Y.S.齐格勒，M.A.戈罗夫斯基，和J.B.奥尔姆斯特德，1982年，《细胞》，31:131 - 136）证明了一种大核特异性组蛋白变体hv1的存在，它在几种哺乳动物细胞系的核仁中的小斑点区域富集。这些观察结果表明，这种组蛋白变体在进化中高度保守，可能与活跃转录的序列相关。尽管在营养生长期间大核和小核在结构和功能上有很大差异，但它们是相关的。在接合过程中，即嗜热四膜虫生命周期的有性阶段，小核的合子后分裂产物产生新的小核和大核，而旧的大核移到每个细胞的后部并被消除。在本研究中，我们使用针对hv1的特异性抗血清，通过间接免疫荧光确定了在接合过程中hv1首次出现在发育中的新大核中的时间。在生长、饥饿和年轻的交配细胞（混合相反交配类型后2 - 5小时）中，用针对hv1的亲和纯化抗体只能检测到大核。在旧大核位于细胞中心的细胞中，新形成的大核要么不被染色，要么仅被弱染色。然而，在旧大核已移到细胞后部的细胞中（大约8小时）可以清楚地观察到新大核。在接合后期（10 - 16小时），新大核中hv1染色的强度随时间增加，这与这些核中DNA含量的增加相对应。旧大核中可检测到的hv1在这些核到达后部细胞质后近1小时（大约9 - 10小时）开始消失，有时在这些核从细胞中被消除之前就完全消失了。用[³H]尿苷短暂标记细胞的放射自显影显示，新大核在第二次合子后分裂后很快（大约8小时）就开始合成RNA。在新大核中能清楚检测到hv1的阶段，原基活跃于RNA合成。旧大核中的RNA合成在新大核开始RNA合成时非常接近的时间停止。因此，hv1的添加与一个转录不活跃的生殖细胞核转变为转录活跃的体细胞核密切相关。我们怀疑hv1的添加在……中起基本作用
