Abstract
The eukaryotic ribonucleic acid (RNA) exosome is a versatile multiribonuclease complex that mediates the processing, surveillance, and degradation of virtually all classes of RNA in both the nucleus and cytoplasm. The complex, composed of 10 to 11 subunits, has been widely described in many organisms. Bioinformatic analyses revealed that there may be also an exosome‐like complex in Plasmodium falciparum, a parasite of great importance in public health, with eight predicted subunits having high sequence similarity to their counterparts in yeast and human. In this work, the putative RNA catalytic components, designated as PfRrp4, PfRrp41, PfDis3, and PfRrp6, were identified and systematically analyzed. Quantitative polymerase chain reaction (QPCR) analyses suggested that all of them were transcribed steadily throughout the asexual stage. The expression of these proteins was determined by Western blot, and their localization narrowed to the cytoplasm of the parasite by indirect immunofluorescence. The recombinant proteins of PfRrp41, PfDis3, and PfRrp6 exhibited catalytic activity for single‐stranded RNA (ssRNA), whereas PfRrp4 showed no processing activity of both ssRNA and dsRNA. The identification of these putative components of the RNA exosome complex opens up new perspectives for a deep understanding of RNA metabolism in the malarial parasite P. falciparum.
Highlights
ribonucleic acid (RNA) metabolism is an essential process that most RNA molecules undergo after transcription
Almost all RNA species matured through the posttranscriptional processing of the precursor RNAs, and are transported to specific cellular compartments to function before degradation
Transcriptional analysis of the Plasmodium falciparum RNA exosomal subunits The transcription features of PfRrp4, PfRrp41, PfRrp42, PfDis3, and PfRrp6 during the erythrocyte stages of P. falciparum were successfully determined by quantitative PCR assays
Summary
RNA metabolism is an essential process that most RNA molecules undergo after transcription. Almost all RNA species matured through the posttranscriptional processing of the precursor RNAs, and are transported to specific cellular compartments to function before degradation. The final three (Csl, Rrp, and Rrp40), which contain the RNA binding domains-S1 or S1 and KH domain, form a cap on the top of a hexamer to bridge the interactions between adjacent heterodimers (Liu et al 2006) This elaborate assembly creates a continuous channel stretching across the Exo, which is one of the pathways of target substrates accessing the exoribonuclease active site (Schneider and Tollervey 2014). We systematically characterized the biochemical functions of the RNA exosomes, and identified the architecture and functional mechanisms of the multiple RNase-like complex in P. falciparum
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