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

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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.