Smilenov L B, Mellado W, Rao P H, Sawant S G, Umbricht C B, Sukumar S, Pandita T K
Center for Radiological Research, Columbia University, New York, NY 10032, USA.
Oncogene. 1998 Oct 22;17(16):2137-42. doi: 10.1038/sj.onc.1202138.
Chinese hamster cells frequently have altered karyotypes. To investigate the basis of recent observations that karyotypic alterations are related to telomeric fusions, we asked whether these alterations are due to lack of telomere repeat binding factor/s. Further, Chinese hamster chromosomes contain large blocks of interstitial telomeric repeats, which are preferentially involved in chromosome breakage and exchange, rendering it an interesting model for such studies. Here, we report on the cloning and the chromosomal localization of the Chinese hamster telomere repeat binding factor, chTRF1. The sequence analysis revealed, similar to human TRF1 (hTRF1), an N-terminal acidic domain, a TRF1 specific DNA binding motif and a C-terminal Myb type domain. Unlike mouse TRF1 (mTRF1), chTRF1 shows 97.5% identity to hTRF1. chTRF1 gene was localized on the long arm of chromosome 5. In vitro translation of chTRF1 resulted in protein product similar in molecular weight to hTRF1. Immunostaining of Chinese hamster ovary cells (CHO) with anti-TRF1 antibody revealed punctate nuclear staining. At metaphase, antibodies failed to detect TRF1 on most of the chromosome ends and the interstitial telomeric repeat bands. These studies suggest that chTRF1 does not bind the interstitial telomeric repeats, and its presence at the metaphase chromosome ends is limited. The later could be a factor contributing to frequent karyotypic alterations observed in Chinese hamster cells.
中国仓鼠细胞的核型常常发生改变。为了探究近期关于核型改变与端粒融合相关的观察结果的基础，我们研究了这些改变是否是由于缺乏端粒重复序列结合因子所致。此外，中国仓鼠染色体包含大片的间质端粒重复序列，这些序列优先参与染色体断裂和交换，使其成为此类研究的一个有趣模型。在此，我们报告中国仓鼠端粒重复序列结合因子chTRF1的克隆及染色体定位。序列分析显示，与人类TRF1（hTRF1）相似，chTRF1具有一个N端酸性结构域、一个TRF1特异性DNA结合基序和一个C端Myb型结构域。与小鼠TRF1（mTRF1）不同，chTRF1与hTRF1的同源性为97.5%。chTRF1基因定位于5号染色体长臂。chTRF1的体外翻译产生了分子量与hTRF1相似的蛋白质产物。用抗TRF1抗体对中国仓鼠卵巢细胞（CHO）进行免疫染色，显示出点状核染色。在中期，抗体未能在大多数染色体末端和间质端粒重复带检测到TRF1。这些研究表明，chTRF1不结合间质端粒重复序列，且其在中期染色体末端的存在有限。后者可能是中国仓鼠细胞中观察到频繁核型改变的一个因素。
