Shestakova Elena A, Mansuroglu Zeyni, Mokrani Houda, Ghinea Nicolae, Bonnefoy Eliette
Régulation de la Transcription et Maladies Génétiques, CNRS UPR2228, IFR-95, Université René Descartes, 45 rue des Saints-Pères, 75270 Paris cedex 06, France.
Nucleic Acids Res. 2004 Aug 17;32(14):4390-9. doi: 10.1093/nar/gkh737. Print 2004.
Pericentromeric gamma-satellite DNA is organized in constitutive heterochromatin structures. It comprises a 234 bp sequence repeated several thousands times surrounding the centromeric sequence of all murine chromosomes. Potential binding sites for transcription factor Yin Yang 1 (YY1), a repressor or activator of several cellular and viral genes, are present in pericentromeric gamma-satellite DNA. Using gel retardation and chromatin immunoprecipitation, we demonstrate in this work that YY1 specifically interacts in vitro and in vivo with gamma-satellite DNA. Using immunoFISH and confocal microscopy we show that YY1 specifically co-localizes with pericentromeric gamma-satellite DNA clusters organized in constitutive heterochromatin in murine L929 and 3T3 fibroblasts cell lines. Immunoelectron microscopy experiments further confirmed YY1 localization in heterochromatic areas. Overall, our results demonstrate for the first time that a fraction of YY1 is directly associated with constitutive heterochromatin structures. This association appears physiologically relevant since the association of YY1 with pericentromeric gamma-satellite DNA observed in cycling 3T3 fibroblasts strongly diminished in quiescent (G0) 3T3 fibroblasts. We discuss the implications of these results in the context of heterochromatin formation as well as with regard to the YY1-induced repression of euchromatic genes.
着丝粒周围的γ-卫星DNA以组成型异染色质结构组织。它由一个234 bp的序列组成，该序列在所有小鼠染色体的着丝粒序列周围重复数千次。转录因子阴阳1（YY1）是几种细胞和病毒基因的抑制因子或激活因子，其潜在结合位点存在于着丝粒周围的γ-卫星DNA中。在这项工作中，我们使用凝胶阻滞和染色质免疫沉淀技术证明YY1在体外和体内与γ-卫星DNA特异性相互作用。使用免疫荧光原位杂交和共聚焦显微镜，我们表明YY1在小鼠L929和3T3成纤维细胞系中与组成型异染色质中组织的着丝粒周围γ-卫星DNA簇特异性共定位。免疫电子显微镜实验进一步证实了YY1在异染色质区域的定位。总体而言，我们的结果首次证明一部分YY1与组成型异染色质结构直接相关。这种关联似乎具有生理相关性，因为在循环的3T3成纤维细胞中观察到的YY1与着丝粒周围γ-卫星DNA的关联在静止（G0）的3T3成纤维细胞中大大减弱。我们在异染色质形成的背景下以及关于YY1诱导的常染色质基因抑制方面讨论了这些结果的意义。
