Cenci Giovanni, Siriaco Giorgia, Gatti Maurizio
Dipartimento di Genetica e Biologia Molecolare, Università di Roma La Sapienza, Piazzale A. Moro, 5, 00185 Rome, Italy.
Genetica. 2003 Mar;117(2-3):311-8. doi: 10.1023/a:1022972902263.
Drosophila telomeres contain multiple copies of HeT-A and TART retrotransposons. These elements specifically transpose to chromosomal ends, compensating for loss of terminal nucleotides that occurs at each cycle of DNA replication. We have investigated the role of these sequences in the formation of telomere-telomere attachments induced by mutations in the UbcD1 gene. We have constructed UbcD1 mutant males carrying terminally deleted X chromosomes devoid of both HeT-A and TART sequences. Cytological analysis of larval neuroblasts from these males revealed that telomeres lacking HeT-A and TART and normal telomeres that contain these sequences participate in telomeric fusions with comparable frequencies. These results indicate that the UbcD1 substrate(s) binds chromosomal termini in a sequence-independent manner. Previous studies have shown that the telomere-capping protein HP1 also binds telomeres lacking HeT-A and TART. Taken together, these findings strongly suggest that the assembly of DNA-protein complexes that protect chromosome ends from fusions do not require specific terminal sequences.
果蝇端粒包含多个HeT - A和TART逆转座子拷贝。这些元件特异性地转座到染色体末端，补偿在DNA复制的每个周期发生的末端核苷酸丢失。我们研究了这些序列在由UbcD1基因突变诱导的端粒 - 端粒连接形成中的作用。我们构建了携带末端缺失的X染色体的UbcD1突变雄性果蝇，该X染色体既没有HeT - A序列也没有TART序列。对这些雄性果蝇幼虫神经母细胞的细胞学分析表明，缺乏HeT - A和TART的端粒以及含有这些序列的正常端粒以相当的频率参与端粒融合。这些结果表明，UbcD1底物以序列非依赖的方式结合染色体末端。先前的研究表明，端粒封端蛋白HP1也结合缺乏HeT - A和TART的端粒。综上所述，这些发现强烈表明，保护染色体末端免于融合的DNA - 蛋白质复合物的组装不需要特定的末端序列。
