Kepten Eldad, Weron Aleksander, Bronstein Irena, Burnecki Krzysztof, Garini Yuval
Physics Department & Institute of Nanotechnology, Bar Ilan University, Ramat Gan, Israel.
Hugo Steinhaus Center, Department of Mathematics, Wroclaw University of Technology, Wroclaw, Poland.
Biophys J. 2015 Oct 6;109(7):1454-62. doi: 10.1016/j.bpj.2015.07.031.
Internal organization and dynamics of the eukaryotic nucleus have been at the front of biophysical research in recent years. It is believed that both dynamics and location of chromatin segments are crucial for genetic regulation. Here we study the relative motion between centromeres and telomeres at various distances and at times relevant for genetic activity. Using live-imaging fluorescent microscopy coupled to stochastic analysis of relative trajectories, we find that the interlocus motion is distance-dependent with a varying fractional memory. In addition to short-range constraining, we also observe long-range anisotropic-enhanced parallel diffusion, which contradicts the expectation for classic viscoelastic systems. This motion is linked to uniform expansion and contraction of chromatin in the nucleus, and leads us to define and measure a new (to our knowledge) uniform contraction-expansion diffusion coefficient that enriches the contemporary picture of nuclear behavior. Finally, differences between loci types suggest that different sites along the genome experience distinctive coupling to the nucleoplasm environment at all scales.
近年来，真核细胞核的内部组织和动态变化一直是生物物理研究的前沿领域。人们认为染色质片段的动态变化和位置对于基因调控至关重要。在此，我们研究了在与基因活性相关的不同距离和时间下，着丝粒和端粒之间的相对运动。通过将实时成像荧光显微镜与相对轨迹的随机分析相结合，我们发现基因座间的运动与距离相关，且具有不同的分数记忆。除了短程约束外，我们还观察到长程各向异性增强的平行扩散，这与经典粘弹性系统的预期相悖。这种运动与细胞核中染色质的均匀膨胀和收缩有关，并引导我们定义和测量了一个新的（据我们所知）均匀收缩-膨胀扩散系数，这丰富了当前对核行为的认识。最后，不同基因座类型之间的差异表明，基因组上的不同位点在所有尺度上与核质环境的耦合方式都有所不同。
