Identification of host RNAs that interact with EBV noncoding RNA EBER2

Mapping of Influenza Virus RNA-RNA Interactions Reveals a Flexible Network

Selective assembly of influenza virus segments into virions is proposed to be mediated through intersegmental RNA-RNA interactions. Here, we developed a method called 2CIMPL that includes proximity ligation under native conditions to identify genome-wide RNA duplexes. Interactions between all eight segments were observed at multiple sites along a given segment and are concentrated at hotspots. Furthermore, synonymous nucleotide changes in a hotspot decreased the formation of RNA-RNA interactions at this site and resulted in a genome-wide rearrangement without a loss in replicative fitness. These results indicate that the viral RNA interaction network is flexible to account for nucleotide evolution. Moreover, comparative analysis of RNA-RNA interaction sites with viral nucleoprotein (NP) binding to the genome revealed that RNA junctions can also occur adjacent to NP peaks, suggesting that NP association does not exclude RNA duplex formation. Overall, 2CIMPL is a versatile technique to map in vivo RNA-RNA interactions.

The many ways Epstein-Barr virus takes advantage of the RNA tool kit

Epstein-Barr virus (EBV) was the first human cancer-causing virus to be discovered over fifty years ago. Given its relatively large genome size for a virus and hence the capacity to store more than mere protein-coding information, EBV also harbours genetic material for producing an array of distinct noncoding (nc)RNAs. The double-stranded nature of its DNA genome allows the utilization of the whole gamut of ncRNA types, including both RNA polymerase II and III transcripts, in devising a sophisticated strategy to ensure its replication upon infection in host cells and evasion of host immune responses. Owing to the development of sensitive technologies in recent years, mostly entailing next-generation sequencing, the list of ncRNA types generated by EBV has expanded now to include two RNAs (EBER1 and EBER2) best categorized as long ncRNAs, dozens of microRNAs, one small nucleolar RNA, stable intronic sequence RNAs, and the most recently discovered circular RNAs. With the application of cutting-edge technology, the molecular mechanisms of some of these noncoding transcripts are beginning to emerge, while others remain yet to be elucidated. As viruses often take advantage of existing molecular pathways established by the host, it is likely that further novel concepts of the greatly unexplored noncoding world can be learned from studying the many EBV ncRNAs.

RNA matchmaking in chromatin regulation

Beyond being the product of gene expression, RNA can also influence the regulation of chromatin. The majority of the human genome has the capacity to be transcribed and the majority of the non-protein-coding transcripts made by RNA Polymerase II are enriched in the nucleus. Many chromatin regulators can bind to these ncRNAs in the nucleus; in some cases, there are clear examples of direct RNA-mediated chromatin regulation mechanisms stemming from these interactions, while others have yet to be determined. Recent studies have highlighted examples of chromatin regulation via RNA matchmaking, a term we use broadly here to describe intermolecular base-pairing interactions between one RNA molecule and an RNA or DNA match. This review provides examples of RNA matchmaking that regulates chromatin processes and summarizes the technical approaches used to capture these events.

5-methylcytosine modification of an Epstein-Barr virus noncoding RNA decreases its stability

Many cellular noncoding RNAs contain chemically modified nucleotides that are essential for their function. The Epstein-Barr virus expresses two highly abundant noncoding RNAs called EBV-encoded RNA 1 (EBER1) and EBER2. To examine whether these viral RNAs contain modified nucleotides, we purified native EBERs from EBV-infected cells and performed mass spectrometry analysis. While EBER2 contains no modified nucleotides at stoichiometric amounts, EBER1 was found to carry 5-methylcytosine (m⁵C) modification. Bisulfite sequencing indicated that a single cytosine of EBER1 is methylated in ∼95% of molecules, and the RNA methyltransferase NSUN2 was identified as the EBER1-specific writer. Intriguingly, ablation of NSUN2 and thus loss of m⁵C modification resulted in an increase in EBER1 levels. We further found that EBER1 is a substrate for the RNase Angiogenin and cleavage in vivo is dependent on the presence of m⁵C, providing an explanation as to why loss of m⁵C increases EBER1 levels. Taken together, our observations indicate that m⁵C, a modification previously shown for tRNAs to oppose Angiogenin-mediated degradation, can also adversely affect RNA stability.

Transcriptome analysis reveals significant differences between primary plasma cell leukemia and multiple myeloma even when sharing a similar genetic background

Primary plasma cell leukemia (pPCL) is a highly aggressive plasma cell dyscrasia characterised by short remissions and very poor survival. Although the 17p deletion is associated with poor outcome and extramedullary disease in MM, its presence does not confer the degree of aggressiveness observed in pPCL. The comprehensive exploration of isoform expression and RNA splicing events may provide novel information about biological differences between the two diseases. Transcriptomic studies were carried out in nine newly diagnosed pPCL and ten MM samples, all of which harbored the 17p deletion. Unsupervised cluster analysis clearly distinguished pPCL from MM samples. In total 3584 genes and 20033 isoforms were found to be deregulated between pPCL and MM. There were 2727 significantly deregulated isoforms of non-differentially expressed genes. Strangely enough, significant differences were observed in the expression of spliceosomal machinery components between pPCL and MM, in respect of the gene, isoform and the alternative splicing events expression. In summary, transcriptome analysis revealed significant differences in the relative abundance of isoforms between pPCL and MM, even when they both had the 17p deletion. The mRNA processing pathway including RNA splicing machinery emerged as one of the most remarkable mechanisms underlying the biological differences between the two entities.

Teaching an Old Virus New Tricks: A Review on New Approaches to Study Age-Old Questions in Influenza Biology

Influenza viruses have been studied for over 80 years, yet much about the basic viral lifecycle remain unknown. However, new imaging, biochemical, and sequencing techniques have revealed significant insight into many age-old questions of influenza virus biology. In this review, we will cover the role of imaging techniques to describe unique aspects of influenza virus assembly, biochemical techniques to study viral genomic organization, and next-generation sequencing to explore influenza genomic evolution. Our goal is to provide a brief overview of how emerging techniques are being used to answer basic questions about influenza viruses. This is not a comprehensive list of emerging techniques, rather ones that we feel will continue to make significant contributions to field of influenza biology.