Nature：揭开姐妹染色体分离的谜团
生物谷配图
生物谷报道： 细胞在有丝分裂和减数分裂过程中，姐妹染色体必需完成分离。姐妹染色体相连的部位称为着丝点。在动物细胞分裂过程中，着丝点被磷酸化从而促进染色体分开，然而中心粒的着丝点是被一种叫shugoshin蛋白保护着的，那么姐妹染色体如何脱离shugoshin蛋白的保护而分开呢，这一机制一直不清楚。
日本科学家以及英、日、澳等国科学家在今天刚刚出版的Nature（5月5日）上给出了答案。一种丝/苏氨酸蛋白磷酸酶2A（PP2A）与人类的shugoshin蛋白相偶联，从而控制着在细胞分裂过程中姐妹染色体分离。在裂殖酵母的研究中，同样发现相似的现象，shugoshin蛋白与PP2A以及Rec8三种蛋白共同包含在着丝点中，调节染色体的分离。
原始出处：
Shugoshin collaborates with protein phosphatase 2A to protect cohesin p46
Tomoya S. Kitajima, Takeshi Sakuno, Kei-ichiro Ishiguro, Shun-ichiro Iemura, Tohru Natsume, Shigehiro A. Kawashima and Yoshinori Watanabe. Nature 441, 46-52 (4 May 2006)
Abstract | Full Text | PDF (778K) | Supplementary information
Protein phosphatase 2A protects centromeric sister chromatid cohesion during meiosis I p53
Christian G. Riedel, Vittorio L. Katis, Yuki Katou, Saori Mori, Takehiko Itoh, Wolfgang Helmhart, Marta Gálová, Mark Petronczki, Juraj Gregan, Bulent Cetin, Ingrid Mudrak, Egon Ogris, Karl Mechtler, Laurence Pelletier, Frank Buchholz, Katsuhiko Shirahige and Kim Nasmyth.Nature 441, 53-61 (4 May 2006)
Abstract | Full Text | PDF (1,400K) | Supplementary information
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减数分裂示意图
Legend:
Illustration of the process by which a single parent diploid cell (Both homologous chromosomes) divides to produce four daughter haploids cells (One homologous chromosome of the pair).
Meiosis is the type of cell division by which germ cells (eggs and sperm) are produced. Meiosis involves a reduction in the amount of genetic material.
Meiosis comprises two successive nuclear divisions with only one round of DNA replication.
Four stages can be described for each nuclear division.
- Interphase: Before meiosis begins, genetic material is duplicated.
- First division of meiosis
- Prophase 1: Duplicated chromatin condenses. Each chromosome consists of two, closely associated sister chromatids. Crossing-over can occur during the latter part of this stage.
- Metaphase 1: Homologous chromosomes align at the equatorial plate.
- Anaphase 1: Homologous pairs separate with sister chromatids remaining together.
- Telophase 1: Two daughter cells are formed with each daughter containing only one chromosome of the homologous pair.
- Second division of meiosis: Gamete formation
- Prophase 2: DNA does not replicate.
- Metaphase 2: Chromosomes align at the equatorial plate.
- Anaphase 2: Centromeres divide and sister chromatids migrate separately to each pole.
- Telophase 2: Cell division is complete. Four haploid daughter cells are obtained.
One parent cell produces four daughter cells. Daughter cells have half the number of chromosomes found in the original parent cell and with crossing over, are genetically different.
Meiosis differs from mitosis primarily because there are two cell divisions in meiosis, resulting in cells with a haploid number of chromosomes.
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