A Novel Role for the 3′-5′ Exoribonuclease Dis3L2 in Controlling Cell Proliferation and Tissue Growth

In a complex organism, cell proliferation and apoptosis need to be precisely controlled in order for tissues to develop correctly. Excessive cell proliferation can lead to diseases such as cancer. We have shown that the exoribonuclease Dis3L2 is required for the correct regulation of proliferation in a natural tissue within the model organism <i>Drosophila melanogaster</i>. Dis3L2 is a member of a highly conserved family of exoribonucleases that degrade RNA in a 3′-5′ direction. We show that knockdown of <i>dis3L2</i> in the <i>Drosophila</i> wing imaginal discs results in substantial wing overgrowth due to increased cellular proliferation rather than an increase in cell size. Imaginal discs are specified in the embryo before proliferating and differentiating to form the adult structures of the fly. Using RNA-seq we identified a small set of mRNAs that are sensitive to Dis3L2 activity. Of the mRNAs which increase in levels and are therefore potential targets of Dis3L2, we identified two that change at the post-transcriptional level but not at the transcriptional level, namely <i>CG2678</i> (a transcription factor) and <i>pyrexia</i> (a TRP cation channel). We also demonstrate a compensatory effect between Dis3L2 and the 5′-3′ exoribonuclease Pacman demonstrating that these two exoribonucleases function to regulate opposing pathways within the developing tissue. This work provides the first description of the molecular and developmental consequences of Dis3L2 inactivation in a non-human animal model. The work is directly relevant to the understanding of human overgrowth syndromes such as Perlman syndrome.

在复杂生物体中，细胞增殖与细胞凋亡需受到精确调控，以保障组织正常发育。细胞过度增殖可引发癌症等多种疾病。我们的研究表明，外切核糖核酸酶（exoribonuclease）Dis3L2是模式生物黑腹果蝇（Drosophila melanogaster）天然组织中增殖调控所必需的因子。Dis3L2属于一类高度保守的外切核糖核酸酶家族，该家族酶可通过3′→5′方向降解RNA。我们发现，在果蝇（Drosophila）翅成虫盘（wing imaginal discs）中敲低dis3L2基因，会导致翅膀显著过度生长，这一现象源于细胞增殖水平提升而非细胞体积增大。成虫盘在胚胎阶段即已特化，后续通过增殖与分化形成果蝇的成体结构。我们通过RNA测序（RNA-seq）技术，筛选出一组对Dis3L2活性敏感的mRNA。在表达水平上调、因此可能是Dis3L2潜在靶标的mRNA中，我们鉴定出两个仅在转录后水平发生变化、而非转录水平变化的基因，分别为CG2678（编码转录因子（transcription factor））与pyrexia（编码TRP阳离子通道（TRP cation channel））。我们还证实，Dis3L2与5′→3′外切核糖核酸酶Pacman之间存在补偿效应，表明这两种外切核糖核酸酶可在发育组织中分别调控相互拮抗的通路。本研究首次在非人类动物模型中阐述了Dis3L2失活所带来的分子与发育层面后果。该研究成果对于理解Perlman综合征等人类过度生长综合征具有直接参考价值。