Zink D, Bornfleth H, Visser A, Cremer C, Cremer T
Institut für Anthropologie und Humangenetik, LMU München, Goethestrasse 31, München, D-80336, Germany.
Exp Cell Res. 1999 Feb 25;247(1):176-88. doi: 10.1006/excr.1998.4311.
It has been suggested that DNA organized into replication foci during S-phase remains stably aggregated in non-S-phase cells and that these stable aggregates provide fundamental units of nuclear or chromosome architecture [C. Meng and R. Berezney (1991) J. Cell Biol. 115, 95a; E. Sparvoli et al. (1994) J. Cell Sci. 107, 3097-3103; D. A. Jackson and A. Pombo (1998) J. Cell Biol. 140, 1285-1295; D. Zink et al. (1998) Hum. Genet. 112, 241-251]. To test this hypothesis, early and late replicating DNA of human diploid fibroblasts was labeled specifically by incorporating two different thymidine analogs [J. Aten (1992) Histochem. J. 24, 251-259; A. E. Visser (1998) Exp. Cell Res. 243, 398-407], during distinct time segments of S-phase. On mitotic chromosomes the amount and spatial distribution of early and late replicating DNA corresponded to R/G-banding patterns. After labeling cells were grown for several cell cycles. During this growth period individual replication labeled chromosomes were distributed into an environment of unlabeled chromosomes. The nuclear territories of chromosomes 13 and 15 were identified by additional chromosome painting. The distribution of early and late replicating DNA was analyzed for both chromosomes in quiescent (G0) cells or at G1. Early and late replicating DNA occupied distinct foci within chromosome territories, displaying a median overlap of only 5-10%. There was no difference in this regard between G1 and G0 cells. Chromosome 13 and 15 territories displayed a similar structural rearrangement in G1 cells compared to G0 cells resulting in the compaction of the territories. The findings demonstrate that early and late replicating foci are maintained during subsequent cell cycles as distinctly separated units of chromosome organization. These findings are compatible with the hypothesis that DNA organized into replicon clusters remains stably aggregated in non-S-phase cells.
有人提出，在S期组织成复制焦点的DNA在非S期细胞中保持稳定聚集，并且这些稳定聚集物提供了核或染色体结构的基本单位[C. Meng和R. Berezney（1991年）《细胞生物学杂志》115, 95a；E. Sparvoli等人（1994年）《细胞科学杂志》107, 3097 - 3103；D. A. Jackson和A. Pombo（1998年）《细胞生物学杂志》140, 1285 - 1295；D. Zink等人（1998年）《人类遗传学》112, 241 - 251]。为了验证这一假设，通过在S期的不同时间段掺入两种不同的胸苷类似物[J. Aten（1992年）《组织化学杂志》24, 251 - 259；A. E. Visser（1998年）《细胞研究实验》243, 398 - 407]，特异性标记了人二倍体成纤维细胞的早期和晚期复制DNA。在有丝分裂染色体上，早期和晚期复制DNA的数量和空间分布与R/G带型模式相对应。标记细胞后让其生长几个细胞周期。在此生长期间，单个复制标记的染色体被分布到未标记染色体的环境中。通过额外的染色体描绘鉴定了13号和15号染色体的核区域。分析了静止（G0）细胞或G1期这两条染色体上早期和晚期复制DNA的分布。早期和晚期复制DNA在染色体区域内占据不同的焦点，显示出仅5 - 10%的中位重叠率。在这方面，G1细胞和G0细胞之间没有差异。与G0细胞相比，13号和15号染色体区域在G1细胞中显示出类似的结构重排，导致区域压缩。这些发现表明，早期和晚期复制焦点在随后的细胞周期中作为染色体组织的明显分离单位得以维持。这些发现与DNA组织成复制子簇在非S期细胞中保持稳定聚集的假设相一致。
