Telomere Structure In Drosophila

我们对端粒结构和特性的遗传控制感兴趣，并将重点放在模式生物--黑腹果蝇上。这种生物体中的端粒是通过三个线状转座子、转座子和基因转换的靶向逆转录转座来维持的。已知这种生物体中的突变会极大地增加或减少端粒特异的反转录转座子在染色体末端的添加频率，这表明这一过程是受基因控制的。我们已经确定了一个基因，端粒延长(TEL)，它的突变增加了末端基因转换和靶向转座的频率，并正在使用位置信息来克隆该基因。TEL基因位于3号染色体右臂中部，位于INO80基因的一个内含子内，大约10kb，与同一内含子中的其他5个基因相近。观察到TEL突变在遗传上是显性的，该区域的缺失没有端粒延长表型，这表明这些突变是功能获得突变，可能位于控制区。对突变体进行了深度测序，并与180株端粒较短的野生型菌株进行了比较，发现该内含子区域存在一个3个碱基对的短缺失。这项分析还在180个端粒异常长的对照菌株中发现了三个新的变异菌株。 染色质结构可以通过控制端粒逆转座子的转录和控制逆转录元件到染色体末端的可及性来调节端粒长度。我们已经启动了一个项目，用转录基因标记端粒特异的HET-A转座元件，以便在转座子从染色体的一端移动到另一端时跟随转座子。HET-A元件被构建在EPgy2转座子内，并插入到苍蝇的基因组中，以检测体内的转座。如果检测有效，它将使我们能够调查什么遗传和环境因素影响移动速度，无论是通过经典的逆转录转座还是通过端粒基因转换。 HET-A元件编码的Gag样蛋白的质谱分析显示，丝氨酸216和221发生了磷酸化。这些修饰似乎对蛋白质的稳定性起到了作用。

We are interested in the genetic control of telomere structure and identity, and have focused on the model organism, Drosophila melanogaster. Telomeres in this organism are maintained by a combination of targeted retrotransposition of three LINE-like, transposons and gene conversion. Mutations in this organism are known that drastically increase or decrease the frequency of additions of telomere-specific retrotransposon to a chromosome end, suggesting that this process is under genetic control. We have identified one gene, Telomere elongation (Tel), which has mutations that increase the frequencies of both terminal gene conversion and targeted transposition, and are using positional information to clone the gene. The Tel gene maps to the middle of right arm of chromosome 3 to a region of approximately 10 kb, inside an intron for the gene Ino80 and near five other genes in the same intron. The observations that the Tel mutations are genetically dominant and that deletions for the region do not have a telomere elongation phenotype suggest that the mutations are gain-of-function mutations and may be in controlling regions. Deep sequencing the mutant and comparison with 180 wild type strains with short telomeres identified a single short, 3 bp deletion in this intronic region. This analysis also identified three new variant strains among the 180 control strains that have exceptionally long telomeres. Chromatin structure may regulate telomere length by controlling transcription of the telomeric retrotransposons and by controlling accessibility of the retroelements to the chromosome end. We have initiated a project to mark a telomere-specific HeT-A transposable element with a transcribed gene in order to follow the transposon as it moves from one chromosome end to another. A HeT-A element has been constructed inside a EPgy2 transposon and inserted into the genome of a fly to assay transposition in vivo. If the assay works, it will allow us to investigate what genetic and environmental factors influence the rate of movement, either by classical retrotransposition or by telomeric gene conversion. Mass spectrometry of the Gag-like protein encoded by the HeT-A element reveals phosphorylation at serines 216 and 221. These modifications appear to play a role in protein stability.