Wang Y, Zhao J, Clapper J, Martin L D, Du C, DeVore E R, Harkins K, Dobbs D L, Benbow R M
Department of Zoology and Genetics, Iowa State University, Ames 50011.
Exp Cell Res. 1995 Mar;217(1):84-91. doi: 10.1006/excr.1995.1066.
The plant amino acid mimosine has been reported to block cell cycle progression and DNA replication in cultured mammalian cells, perhaps by blocking initiation. In this study, we show that mimosine does not block initiation or any other step in DNA replication in embryonic cells of Xenopus laevis. Mimosine does not block DNA replication in cell-free "cycling" extracts of Xenopus eggs, nor does it block M to S phase transition in cell-free egg extracts released from metaphase arrest. Microinjection of mimosine into 4-cell embryos had no visible effect on development during the first 3 days after fertilization. Prior to the midblastula transition, when the cell cycle consists of alternating S and M phases, neither chromosomal DNA replication nor replication of microinjected plasmid DNA were inhibited by mimosine microinjected into cleaving Xenopus embryos. Microinjection of mimosine after the midblastula transition, when large endogenous stockpiles of DNA replication components have begun to be depleted and Xenopus embryonic cells have acquired G1 and G2 phases, still did not inhibit cell cycle progression or DNA replication. In marked contrast, mimosine arrested the growth of proliferating cultured Xenopus kidney epithelial A6 cells near the G1/S boundary. We conclude that mimosine appears to block DNA replication and cell cycle progression in somatic cells, but has no apparent effect in rapidly dividing Xenopus embryonic cells.
据报道，植物氨基酸含羞草素可阻断培养的哺乳动物细胞的细胞周期进程和DNA复制，可能是通过阻断起始过程来实现的。在本研究中，我们发现含羞草素并不会阻断非洲爪蟾胚胎细胞DNA复制的起始或任何其他步骤。含羞草素不会阻断非洲爪蟾卵的无细胞“循环”提取物中的DNA复制，也不会阻断从中期阻滞释放的无细胞卵提取物中从M期到S期的转变。将含羞草素显微注射到4细胞胚胎中，在受精后的前3天对发育没有明显影响。在囊胚中期转变之前，当细胞周期由交替的S期和M期组成时，显微注射到正在分裂的非洲爪蟾胚胎中的含羞草素既不会抑制染色体DNA复制，也不会抑制显微注射的质粒DNA的复制。在囊胚中期转变之后进行含羞草素显微注射，此时DNA复制成分的大量内源性储备已开始耗尽，非洲爪蟾胚胎细胞已获得G1期和G2期，但仍不会抑制细胞周期进程或DNA复制。与之形成鲜明对比的是，含羞草素使增殖的培养非洲爪蟾肾上皮A6细胞在G1/S边界附近的生长停滞。我们得出结论，含羞草素似乎会阻断体细胞中的DNA复制和细胞周期进程，但对快速分裂的非洲爪蟾胚胎细胞没有明显影响。
