Single molecule nanoscopy reveals that nuclear myosin VI regulates the spatial organization of mammalian transcription initiation

During transcription, RNA Polymerase II (RNAPII) is spatially organised into clusters that correlate with transcription activity. However, the assembly, organisation and stability of these transcription units remains unknown. Here, we have combined single molecule imaging with genomics approaches in order to explore the role of nuclear myosin VI in the nanoscale organisation of RNAPII. We can reveal that myosin VI acts as the molecular anchor that holds RNAPII into these transcription factories. Perturbation of myosin VI leads to the disruption of RNAPII localisation, changes in chromatin organisation and subsequently a decrease in gene expression. This role of Myosin VI is particularly important for transcription events following stimulation, where multiple genes are simultaneously activated. Total RNA was extracted from three replicates of WT, MVI KD and Scrambled siRNA Hela cells.

在转录过程中，RNA聚合酶II（RNA Polymerase II，RNAPII）会在空间上聚集形成簇结构，且该簇与转录活性密切相关。然而，此类转录单元的组装机制、组织形式及稳定性仍未阐明。本研究将单分子成像（single molecule imaging）技术与基因组学方法相结合，旨在探究核肌球蛋白VI（nuclear myosin VI）在RNA聚合酶II纳米级组织中的调控作用。研究结果表明，肌球蛋白VI可作为分子锚点，将RNA聚合酶II锚定在这些转录工厂（transcription factories）中。对肌球蛋白VI的扰动会破坏RNA聚合酶II的定位，改变染色质（chromatin）的组织构象，并最终导致基因表达水平下调。肌球蛋白VI的这一功能在刺激后的转录事件中尤为关键，此时多个基因会被同步激活。本研究从野生型（Wild Type，WT）、肌球蛋白VI敲低（Myosin VI Knockdown，MVI KD）以及阴性对照siRNA（Scrambled siRNA）处理的海拉（Hela）细胞的三个生物学重复样本中提取了总RNA。