摘要
人类Ｔ淋巴细胞白血病基因家族（Ｔｃｅｌｌｔｒａｎｓｌｏｃａｔｉｏｎｇｅｎｅ，简称ＴＴＧ，或Ｒｈｏｍｂｏｔｉｎ，简称ＲＢＴＮ）是一个肿瘤基因家族，包括有３个基因：ＴＴＧ－１／ＲＢＴＭ－１、ＴＴＧ－２／ＲＢＴＮ－２、ＴＴＧ－３／ＲＢＴＮ－３。其中ＴＴＧ－１和ＴＴＧ－２是分别在二个具有不同染色体易位的Ｔ淋巴细胞白血病人中克隆到的。这个基因家族共同含有一个ＬＩＭ结构，这个ＬＩＭ结构编码一个二次重复出现的富含半胱氨酸的保守区域，而这个结构的功能至今不详。在发现原癌基因ＴＴＧ－２在哺乳动物、果蝇和酵母中高度保守后，为了研究ＬＩＭ结构的功能取得一个模式系统，首先在果蝇基因组文库中克隆到了果蝇与人类ＴＴＧ家族同源的果蝇ｔｔｇ基因，证实在果蝇体内只有一个ｔｔｇ基因（即Ｄｒｏｓｏｐｈｉｌａｔｔｇ简称ｄｔｔｇ）。这个基因的ｃＤＮＡ克隆全长２０８７ｂｐ，编码一个２６６个氨基酸的肽链。５＇端有二种不同的剪接方式。并且ｄｔｔｇ蛋白也含有一个二次重复的保守的ＬＩＭ结构。ｄｔｔｇ外显子的结构与人类的ＴＴＧ－１更接近，ＬＩＭＩ是一个外显子，ＬＩＭ２被一个内含子分隔为二个外显子。在氨基酸序列上ｄｔｔｇ与ＴＴＧ－１有７９％的同源性，与ＴＴＧ－２?
The human TTG/RBTN family is an oncogene family. There are three members in this family: TTG-1/RBTN-1; TTG-2/RBTN-2 and TTG-3/RBTNL-3. Two of them, TTG-1/RBTN-1 and TTG-2/RBTN-2 have been isolated at the sites of chromosomal translocations in T-cell leukaemia. This gene family encodes cysteine-rich proteins with two tandem copies of a LIM motif. The function of the LIM motifis unknown.We found that the TTG-2gene is highly conserved among mammals, Drosophila and yeast. As a first step to obtain a model system for studying the function of the LIM motifs, we isolated the Drosophila homologue dttg. In contrast to human, Drosophila appeared to have only one ttg/rbtn gene. A2087bp cDNA clone was isolated, encoding a protein of 266 amino acids. A second transcript with an alternative 5'end was identified in RNA from embryos. The Drosophila ttg protein consisted of two tandem copies of the conserved LIM domain characteristic of the human TTG/RBTN family. The amino acid sequence similarity with human TTG-1 and TTG-2 is 79% and 62%, respectively.The dttg,like TTG-1,have an intron in the second LIM encoding region, which is not present in TTG-2.
