Takeshita S, Kikuno R, Tezuka K, Amann E
Hoechst Japan Limited, Pharma Research Laboratories, Saitama.
Biochem J. 1993 Aug 15;294 ( Pt 1)(Pt 1):271-8. doi: 10.1042/bj2940271.
A cDNA library prepared from the mouse osteoblastic cell line MC3T3-E1 was screened for the presence of specifically expressed genes by employing a combined subtraction hybridization/differential screening approach. A cDNA was identified and sequenced which encodes a protein designated osteoblast-specific factor 2 (OSF-2) comprising 811 amino acids. OSF-2 has a typical signal sequence, followed by a cysteine-rich domain, a fourfold repeated domain and a C-terminal domain. The protein lacks a typical transmembrane region. The fourfold repeated domain of OSF-2 shows homology with the insect protein fasciclin I. RNA analyses revealed that OSF-2 is expressed in bone and to a lesser extent in lung, but not in other tissues. Mouse OSF-2 cDNA was subsequently used as a probe to clone the human counterpart. Mouse and human OSF-2 show a high amino acid sequence conservation except for the signal sequence and two regions in the C-terminal domain in which 'in-frame' insertions or deletions are observed, implying alternative splicing events. On the basis of the amino acid sequence homology with fasciclin I, we suggest that OSF-2 functions as a homophilic adhesion molecule in bone formation.
采用消减杂交与差异筛选相结合的方法，对从小鼠成骨细胞系MC3T3-E1构建的cDNA文库进行筛选，以寻找特异性表达的基因。鉴定并测序了一个cDNA，它编码一种名为成骨细胞特异性因子2（OSF-2）的蛋白质，该蛋白质由811个氨基酸组成。OSF-2具有典型的信号序列，其后是富含半胱氨酸的结构域、四重重复结构域和C末端结构域。该蛋白质缺乏典型的跨膜区域。OSF-2的四重重复结构域与昆虫蛋白fasciclin I具有同源性。RNA分析表明，OSF-2在骨组织中表达，在肺组织中表达较少，但在其他组织中不表达。随后，小鼠OSF-2 cDNA被用作探针来克隆人类的对应物。除了信号序列以及在C末端结构域中观察到“框内”插入或缺失的两个区域外，小鼠和人类的OSF-2显示出高度的氨基酸序列保守性，这意味着存在可变剪接事件。基于与fasciclin I的氨基酸序列同源性，我们认为OSF-2在骨形成中作为一种同源性粘附分子发挥作用。
