Lindsay Andrew J, McCaffrey Mary W
Molecular Cell Biology Laboratory, Department of Biochemistry, Biosciences Institute, University College Cork, Cork, Ireland.
Cell Motil Cytoskeleton. 2009 Dec;66(12):1057-72. doi: 10.1002/cm.20408.
It is becoming increasingly clear that the mammalian class V myosins are involved in a wide range of cellular processes such as receptor trafficking, mRNA transport, myelination in oligodendrocytes and cell division. Using paralog-specific antibodies, we observed significant nuclear localisation for both myosin Va and myosin Vb. Myosin Vb was present in nucleoli where it co-localises with RNA polymerase I, and newly synthesised ribosomal RNA (rRNA), indicating that it may play a role in transcription. Indeed, its nucleolar pattern was altered upon treatment with RNA polymerase I inhibitors. In contrast, myosin Va is largely excluded from nucleoli and is unaffected by these inhibitors. Myosin Vb was also found to physically associate with RNA polymerase I and actin in co-immunoprecipitation experiments. We propose that myosin Vb serves a role in rRNA transcription.
越来越明显的是，哺乳动物的V类肌球蛋白参与了广泛的细胞过程，如受体运输、mRNA转运、少突胶质细胞中的髓鞘形成和细胞分裂。使用旁系同源特异性抗体，我们观察到肌球蛋白Va和肌球蛋白Vb都有显著的核定位。肌球蛋白Vb存在于核仁中，与RNA聚合酶I和新合成的核糖体RNA（rRNA）共定位，表明它可能在转录中发挥作用。事实上，用RNA聚合酶I抑制剂处理后，其核仁模式发生了改变。相比之下，肌球蛋白Va在很大程度上被排除在核仁之外，并且不受这些抑制剂的影响。在免疫共沉淀实验中还发现肌球蛋白Vb与RNA聚合酶I和肌动蛋白存在物理关联。我们认为肌球蛋白Vb在rRNA转录中发挥作用。
