Reddy K L, Zullo J M, Bertolino E, Singh H
Howard Hughes Medical Institute, The University of Chicago, GCIS W522, 929 East 57th Street, Chicago, Illinois 60637, USA.
Nature. 2008 Mar 13;452(7184):243-7. doi: 10.1038/nature06727. Epub 2008 Feb 13.
Nuclear compartmentalization seems to have an important role in regulating metazoan genes. Although studies on immunoglobulin and other loci have shown a correlation between positioning at the nuclear lamina and gene repression, the functional consequences of this compartmentalization remain untested. We devised an approach for inducible tethering of genes to the inner nuclear membrane (INM), and tested the consequences of such repositioning on gene activity in mouse fibroblasts. Here, using three-dimensional DNA-immunoFISH, we demonstrate repositioning of chromosomal regions to the nuclear lamina that is dependent on breakdown and reformation of the nuclear envelope during mitosis. Moreover, tethering leads to the accumulation of lamin and INM proteins, but not to association with pericentromeric heterochromatin or nuclear pore complexes. Recruitment of genes to the INM can result in their transcriptional repression. Finally, we use targeted adenine methylation (DamID) to show that, as is the case for our model system, inactive immunoglobulin loci at the nuclear periphery are contacted by INM and lamina proteins. We propose that these molecular interactions may be used to compartmentalize and to limit the accessibility of immunoglobulin loci to transcription and recombination factors.
核区室化似乎在调控后生动物基因方面发挥着重要作用。尽管对免疫球蛋白及其他基因座的研究表明，位于核纤层与基因抑制之间存在关联，但这种区室化的功能后果仍未得到验证。我们设计了一种将基因诱导拴系至内核膜（INM）的方法，并测试了这种重新定位对小鼠成纤维细胞基因活性的影响。在此，我们使用三维DNA免疫荧光原位杂交技术（3D DNA-immunoFISH），证明了染色体区域在有丝分裂期间依赖于核膜的解体和重新形成而重新定位至核纤层。此外，拴系会导致核纤层蛋白和内核膜蛋白的积累，但不会与着丝粒周围异染色质或核孔复合体发生关联。将基因招募至内核膜可导致其转录抑制。最后，我们使用靶向腺嘌呤甲基化（DamID）技术表明，就我们所构建的模型系统而言，位于核周边的无活性免疫球蛋白基因座会与内核膜蛋白和核纤层蛋白发生接触。我们提出，这些分子相互作用可能用于区室化并限制免疫球蛋白基因座与转录和重组因子的可及性。
