Inhibition of homologous recombination by a cohesin-associated clamp complex recruited to the rDNA recombination enhancer
Inhibition of homologous recombination by a cohesin-associated clamp complex recruited to the rDNA recombination enhancer
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DOI：
10.1101/gad.1472706
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发表时间：
2006-10-15
影响因子：
10.5
通讯作者：
Moazed, Danesh
中科院分区：
文献类型：
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作者：
Huang, Julie;Brito, Ilana L.;Moazed, Danesh
酵母核糖体DNA(RDNA)重复序列中的沉默通过抑制超重组和重新抑制外来启动子的转录来保护这个高度重复的阵列的完整性。利用亲和纯化结合高灵敏混合质谱仪，我们分析了参与抑制rDNA基因座内同源重组的蛋白质相互作用网络。我们发现Rent(核仁沉默和末期退出的调节因子)沉默复合体的Net1和Sir2亚单位，以及将Rate招募到rDNA的非转录间隔区(NTS1)的Fob1，在物理上与Tof2相关。除了Rate组分和Fob1外，Tof2还与Lrs4和Csm1组成的两个亚基复合体结合。Tof2、Lrs4和Csm1被Fob1招募到NTS1区域，并且是在该rDNA区域沉默所特需的。此外，Lrs4和Csm1与Sir2协同作用，抑制rDNA上的不等交叉，并在后期从核仁中释放出来。结合先前显示Csm1与粘附素物理结合的观察，这些发现提出了一种可能的模型，在该模型中，Rate、Tof2和Lrs4/Csm1物理地将rDNA夹在粘附素环上，从而限制rDNA姐妹染色单体相对于彼此的运动，以抑制不平等交换。
Silencing within the yeast ribosomal DNA ( rDNA) repeats protects the integrity of this highly repetitive array by inhibiting hyperrecombination and repressing transcription from foreign promoters. Using affinity purification combined with highly sensitive mixture mass spectrometry, we have analyzed the protein interaction network involved in suppressing homologous recombination within the rDNA locus. We show that the Net1 and Sir2 subunits of the RENT (regulator of nucleolar silencing and telophase exit) silencing complex, and Fob1, which recruits RENT to the nontranscribed spacer I (NTS1) region of rDNA, are physically associated with Tof2. In addition to RENT components and Fob1, Tof2 copurified with a two-subunit complex composed of Lrs4 and Csm1. Tof2, Lrs4, and Csm1 are recruited to the NTS1 region by Fob1 and are specifically required for silencing at this rDNA region. Moreover, Lrs4 and Csm1 act synergistically with Sir2 to suppress unequal crossover at the rDNA and are released from the nucleolus during anaphase. Together with previous observations showing that Csm1 physically associates with cohesin, these findings suggest a possible model in which RENT, Tof2, and Lrs4/Csm1 physically clamp rDNA to the cohesin ring, thereby restricting the movement of rDNA sister chromatids relative to each other to inhibit unequal exchange.