Huang Yanmei, McNeil Gerard P, Jackson F Rob
Department of Neuroscience, Sackler School of Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts, United States of America.
Department of Biology, York College, Jamaica, New York, New York, United States of America.
PLoS Genet. 2014 Sep 11;10(9):e1004536. doi: 10.1371/journal.pgen.1004536. eCollection 2014 Sep.
The Drosophila homolog of Casein Kinase I δ/ε, DOUBLETIME (DBT), is required for Wnt, Hedgehog, Fat and Hippo signaling as well as circadian clock function. Extensive studies have established a critical role of DBT in circadian period determination. However, how DBT expression is regulated remains largely unexplored. In this study, we show that translation of dbt transcripts are directly regulated by a rhythmic RNA-binding protein (RBP) called LARK (known as RBM4 in mammals). LARK promotes translation of specific alternative dbt transcripts in clock cells, in particular the dbt-RC transcript. Translation of dbt-RC exhibits circadian changes under free-running conditions, indicative of clock regulation. Translation of a newly identified transcript, dbt-RE, is induced by light in a LARK-dependent manner and oscillates under light/dark conditions. Altered LARK abundance affects circadian period length, and this phenotype can be modified by different dbt alleles. Increased LARK delays nuclear degradation of the PERIOD (PER) clock protein at the beginning of subjective day, consistent with the known role of DBT in PER dynamics. Taken together, these data support the idea that LARK influences circadian period and perhaps responses of the clock to light via the regulated translation of DBT. Our study is the first to investigate translational control of the DBT kinase, revealing its regulation by LARK and a novel role of this RBP in Drosophila circadian period modulation.
酪蛋白激酶Iδ/ε的果蝇同源物DOUBLETIME（DBT）是Wnt、Hedgehog、Fat和Hippo信号通路以及昼夜节律时钟功能所必需的。广泛的研究已经确定DBT在昼夜节律周期确定中起关键作用。然而，DBT的表达是如何调控的，在很大程度上仍未得到探索。在本研究中，我们表明dbt转录本的翻译直接受一种名为LARK（在哺乳动物中称为RBM4）的节律性RNA结合蛋白（RBP）调控。LARK促进时钟细胞中特定的dbt可变转录本的翻译，特别是dbt-RC转录本。在自由运行条件下，dbt-RC的翻译呈现昼夜变化，表明受时钟调控。一种新鉴定的转录本dbt-RE的翻译以LARK依赖的方式被光诱导，并在光/暗条件下振荡。LARK丰度的改变会影响昼夜节律周期长度，并且这种表型可以被不同的dbt等位基因所改变。在主观日开始时，LARK增加会延迟周期蛋白（PER）时钟蛋白的核降解，这与DBT在PER动态中的已知作用一致。综上所述，这些数据支持这样一种观点，即LARK通过对DBT的翻译调控来影响昼夜节律周期，也许还影响时钟对光的反应。我们的研究首次探讨了DBT激酶的翻译控制，揭示了其受LARK调控以及这种RBP在果蝇昼夜节律周期调节中的新作用。
