The Plasmodium falciparum DNA/RNA-binding protein PfAlba1 post-transcriptionally modulates the translational timing of erythrocyte invasion proteins. PfAlba1 modulation of erythrocyte invasion protein translation

In the malaria parasite Plasmodium falciparum, transcriptome-wide ribosome-association studies have suggested that select asexual stage transcripts are translationally regulated. Here, we present insight into the molecular mechanisms that govern this process. We explored the DNA/RNA-binding protein PfAlba1 which localizes to multiple cytoplasmic foci in P. falciparum trophozoites. We affinity-purified PfAlba1-associated RNAs from trophozoites, and using high-throughput sequencing, identified 1193 transcripts that directly bound to PfAlba1. For 105 such transcripts, steady state levels significantly changed upon PfAlba1 overexpression suggesting that PfAlba1 participates in mRNA homeostasis. Additionally, we discovered that binding of PfAlba1 to four erythrocyte invasion mRNAs, Rap1, RhopH3, CDPK1 and AMA1, was linked to translation repression in trophozoites whereas release of these mRNAs from a PfAlba1 complex correlated with protein synthesis in mature schizonts. Together, our results show for the first time that PfAlba1 regulates asexual stage mRNA homeostasis and fine-tunes the translational timing of key P. falciparum erythrocyte invasion transcripts.

针对恶性疟原虫（Plasmodium falciparum），已有全转录组核糖体结合研究（transcriptome-wide ribosome-association studies）提示，部分特定无性期转录本存在翻译调控现象。本研究解析了调控该过程的分子机制。我们对定位于恶性疟原虫滋养体（trophozoites）内多个细胞质灶（cytoplasmic foci）的DNA/RNA结合蛋白（DNA/RNA-binding protein）PfAlba1展开了研究。我们从滋养体中亲和纯化（affinity-purified）了与PfAlba1结合的RNA，并借助高通量测序（high-throughput sequencing）鉴定出1193个可直接与PfAlba1结合的转录本。在105个此类转录本中，当PfAlba1过表达（overexpression）时，其稳态水平（steady state levels）发生显著变化，提示PfAlba1参与mRNA稳态（mRNA homeostasis）的调控。此外，我们发现PfAlba1与4种红细胞入侵（erythrocyte invasion）相关mRNA——Rap1、RhopH3、CDPK1及AMA1的结合，与滋养体阶段的翻译抑制（translation repression）相关；而这些mRNA从PfAlba1复合物中释放，则与成熟裂殖体（mature schizonts）阶段的蛋白质合成（protein synthesis）密切相关。综上，本研究首次证实，PfAlba1可调控恶性疟原虫无性期mRNA稳态，并微调关键红细胞入侵转录本的翻译时序（translational timing）。