Study about Tubulin protein's novel function in interphase nuclei and regulation by polycomb proteins.

在后生动物中，核膜的内表面排列着核层（nuclear lamina， NL），主要由Lamins组成。NL和核内分子的物理相互作用参与染色体陈述和转录活性的调节。大量与NL相关的基因在转录上受到抑制。NL还与包括hdac在内的多种染色质修饰因子相关。鉴于组蛋白在核外围的乙酰化水平较低，且与NL相互作用基因的转录活性密切相关，这些分子关联使得NL近端空间成为一个微域，促进组蛋白去乙酰化，从而抑制转录。然而，在活细胞中连接NL及其结合因子的机制尚不清楚。在这里，我们发现微管蛋白持续与NL结合，并且是NL-染色质和NL- hdac结合所不可或缺的。NL中微管蛋白的缺失导致NL中染色质和HDACs的脱离，以及核外周组蛋白乙酰化的上调。此外，我们发现微管蛋白和染色质的结合需要polycomb group（PcG）蛋白Ring1b，因此Ring1b介导染色质和NL的结合。我们的数据显示了微管蛋白和PcGs在细胞核周围决定染色体陈述的分子组装中的新功能。

In metazoan, the inner surface of nuclear envelope is lined by nuclear lamina(NL), primarily consist of Lamins. Physical interaction of NL and intranuclear molecules engages in regulation of chromosome statement and of transcriptional activity. Large extent of the genes associating to NL is transcriptionally repressed. NL also associates to variety of chromatin modifying factors including HDACs. Given that histone acetylation at nuclear periphery in low level and is close involved in transcriptional activity of genes interacting to NL, these molecular associations make proximal space of NL a microdomain which promotes deacetylation of histone, and thereby transcriptional repression.However, machineries which link NL and its binding factors in living cells are yet poorly understood. Here we show Tubulin proteins persistently associate to NL, and are indispensable for association of NL-chromatin, and of NL-HDACs. Loss of Tubulin from NL results in the disengagement of chromatin and HDACs from NL, and upregulation of histone acetylation at nuclear periphery. Moreover, we found association of Tubulin and chromatin requires polycomb group(PcG) protein Ring1b, therefore Ring1b mediates binding of chromatin and NL. Our data show novel function of Tubulin proteins and PcGs for the molecular assembly determinative for chromosome statement at nuclear periphery.