Reciprocal modulation of long noncoding RNA EMS and p53 regulates tumorigenesis

p53 plays a central role in tumor suppression. Emerging evidence suggests long noncoding RNA (lncRNA) as an important class of regulatory molecules that control the p53 signaling. Here, we report that the oncogenic lncRNA E2F1 messenger RNA (mRNA) stabilizing factor (EMS) and p53 mutually repress each other’s expression. EMS is negatively regulated by p53. As a direct transcriptional repression target of p53, EMS is surprisingly shown to inhibit p53 expression. EMS associates with cytoplasmic polyadenylation element-binding protein 2 (CPEB2) and thus, disrupts the CPEB2–p53 mRNA interaction. This disassociation attenuates CPEB2-mediated p53 mRNA polyadenylation and suppresses p53 translation. Functionally, EMS is able to exert its oncogenic activities, at least partially, via the CPEB2–p53 axis. Together, these findings reveal a double-negative feedback loop between p53 and EMS, through which p53 is finely controlled. Our study also demonstrates a critical role for EMS in promoting tumorigenesis via the negative regulation of p53.

Orb-dependent polyadenylation contributes to PLP expression and centrosome scaffold assembly

As the microtubule-organizing centers (MTOCs) of most cells, centrosomes engineer the bipolar mitotic spindle required for error-free mitosis. Drosophila Pericentrin (PCNT)-like protein (PLP) is a key centrosome component that directs formation of a pericentriolar material (PCM) scaffold required for PCM organization and MTOC function. Here, we investigate the post-transcriptional regulation of plp mRNA. We identify conserved binding sites for cytoplasmic polyadenylation element binding (CPEB) proteins within the plp 3′-untranslated region and examine the role of the CPEB ortholog, oo18 RNA-binding protein (Orb), in plp mRNA regulation. Our data show Orb biochemically interacts with plp mRNA and promotes PLP protein expression. Loss of orb, but not orb2, diminishes PLP levels in embryonic extracts. Consequently, PLP localization to centrosomes and function in PCM scaffolding is compromised in orb mutant embryos, resulting in genome instability and embryonic lethality. Moreover, we find PLP over-expression can restore centrosome scaffolding and rescue the cell division defects caused by orb depletion. Our data suggest Orb modulates PLP expression at the level of plp mRNA polyadenylation and showcases the post-transcriptional regulation of core, conserved centrosomal mRNAs as critical for centrosome function.

Transcriptional dynamics in the protozoan parasite Sarcocystis neurona and mammalian host cells after treatment with a specific inhibitor of apicomplexan mRNA polyadenylation

In recent years, a class of chemical compounds (benzoxaboroles) that are active against a range of parasites has been shown to target mRNA polyadenylation by inhibiting the activity of CPSF73, the endonucleolytic core of the eukaryotic polyadenylation complex. One particular compound, termed AN3661, is active against several apicomplexan parasites that cause disease in humans. In this study, we report that AN3661 is active against an apicomplexan that causes disease in horses and marine mammals (Sarcocystis neurona), with an approximate IC50 value of 14.99 nM. Consistent with the reported mode of action of AN3661 against other apicomplexans, S. neurona mutants resistant to AN3661 had an alteration in CPSF73 that was identical to a mutation previously documented in AN3661-resistant Toxoplasma gondii and Plasmodium falciparum. AN3661 had a wide-ranging effect on poly(A) site choice in S. neurona, with more than half of all expressed genes showing some alteration in mRNA 3’ ends. This was accompanied by changes in the relative expression of more than 25% of S. neurona genes and an overall 5-fold reduction of S. neurona transcripts in infected cells. In contrast, AN3661 had no discernible effect on poly(A) site choice or gene expression in the host cells. These transcriptomic studies indicate that AN3661 is exceedingly specific for the parasite CPSF73 protein, and has the potential to augment other therapies for the control of apicomplexan parasites in domestic animals.

Aurora kinase B inhibits Aurora kinase A to control maternal mRNA translation in mouse oocytes

Mammalian oocytes are transcriptionally quiescent, and meiosis and early embryonic divisions rely on translation of stored maternal mRNAs. Activation of these mRNAs is mediated by polyadenylation. Cytoplasmic polyadenylation binding element 1 (CPEB1) regulates activates mRNA polyadenylation. One message is Aurora kinase C (Aurkc), encoding a protein that regulates chromosome segregation. We previously demonstrated that AURKC levels are upregulated in oocytes lacking Aurora kinase B (AURKB), and this upregulation caused increased aneuploidy rates, a role we investigate here. Using genetic and pharmacologic approaches, we found that AURKB negatively regulates CPEB1-dependent translation of many messages. To determine why translation is increased, we evaluated Aurora kinase A (AURKA), a kinase that activates CPEB1 in other organisms. We find that AURKA activity is increased in Aurkb knockout oocytes and demonstrate that this increase drives the excess translation. Importantly, removal of one copy of Aurka from the Aurkb knockout strain background, reduces aneuploidy rates. This study demonstrates that AURKA is required for CPEB1-dependent translation, and it describes a new AURKB requirement to maintain translation levels through AURKA, a function critical to generating euploid eggs.

PARN-like Proteins Regulate Gene Expression in Land Plant Mitochondria by Modulating mRNA Polyadenylation

Mitochondria have their own double-stranded DNA genomes and systems to regulate transcription, mRNA processing, and translation. These systems differ from those operating in the host cell, and among eukaryotes. In recent decades, studies have revealed several plant-specific features of mitochondrial gene regulation. The polyadenylation status of mRNA is critical for its stability and translation in mitochondria. In this short review, I focus on recent advances in understanding the mechanisms regulating mRNA polyadenylation in plant mitochondria, including the role of poly(A)-specific ribonuclease-like proteins (PARNs). Accumulating evidence suggests that plant mitochondria have unique regulatory systems for mRNA poly(A) status and that PARNs play pivotal roles in these systems.

Advances in the Bioinformatics Knowledge of mRNA Polyadenylation in Baculovirus Genes

Baculoviruses are a group of insect viruses with large circular dsDNA genomes exploited in numerous biotechnological applications, such as the biological control of agricultural pests, the expression of recombinant proteins or the gene delivery of therapeutic sequences in mammals, among others. Their genomes encode between 80 and 200 proteins, of which 38 are shared by all reported species. Thanks to multi-omic studies, there is remarkable information about the baculoviral proteome and the temporality in the virus gene expression. This allows some functional elements of the genome to be very well described, such as promoters and open reading frames. However, less information is available about the transcription termination signals and, consequently, there are still imprecisions about what are the limits of the transcriptional units present in the baculovirus genomes and how is the processing of the 3′ end of viral mRNA. Regarding to this, in this review we provide an update about the characteristics of DNA signals involved in this process and we contribute to their correct prediction through an exhaustive analysis that involves bibliography information, data mining, RNA structure and a comprehensive study of the core gene 3′ ends from 180 baculovirus genomes.