Combier Jean Philippe, de Billy Françoise, Gamas Pascal, Niebel Andreas, Rivas Susana
Laboratoire des Interactions Plantes Micro-organismes (LIPM), Centre National de la Recherche Scientifique-Institut National de la Recherche Agronomique UMR 2594/441, F-31320 Castanet Tolosan, France.
Genes Dev. 2008 Jun 1;22(11):1549-59. doi: 10.1101/gad.461808.
MtHAP2-1 is a CCAAT-binding transcription factor from the model legume Medicago truncatula. We previously showed that MtHAP2-1 expression is regulated both spatially and temporally by microRNA169. Here we present a novel regulatory mechanism controlling MtHAP2-1 expression. Alternative splicing of an intron in the MtHAP2-1 5'leader sequence (LS) becomes predominant during the development of root nodules, leading to the production of a small peptide, uORF1p. Our results indicate that binding of uORF1p to MtHAP2-1 5'LS mRNA leads to reduced accumulation of the MtHAP2-1 transcript and may contribute to spatial restriction of MtHAP2-1 expression within the nodule. We propose that miR169 and uORF1p play essential, sequential, and nonredundant roles in regulating MtHAP2-1 expression. Importantly, in contrast to previously described cis-acting uORFs, uORF1p is able to act in trans to down-regulate gene expression. Our work thus contributes to a better understanding of the action of upstream ORFs (uORFs) in the regulation of gene expression.
MtHAP2-1是来自模式豆科植物蒺藜苜蓿的一种CCAAT结合转录因子。我们之前表明，MtHAP2-1的表达受到微小RNA169在空间和时间上的调控。在此，我们提出一种控制MtHAP2-1表达的新调控机制。MtHAP2-1 5'前导序列（LS）中一个内含子的可变剪接在根瘤发育过程中变得占主导地位，导致产生一种小肽，即上游开放阅读框1肽（uORF1p）。我们的结果表明，uORF1p与MtHAP2-1 5'LS mRNA的结合导致MtHAP2-1转录本积累减少，并可能有助于在根瘤内对MtHAP2-1表达进行空间限制。我们提出，miR169和uORF1p在调控MtHAP2-1表达中发挥重要、相继且非冗余的作用。重要的是，与先前描述的顺式作用上游开放阅读框不同，uORF1p能够反式作用以下调基因表达。因此，我们的工作有助于更好地理解上游开放阅读框（uORFs）在基因表达调控中的作用。
