Sequencing and biological characterization of historical cynosurus mottle virus isolates from Germany.

We report sequencing of four historical cynosurus mottle virus (CnMoV) isolates, originating from different hosts and locations. The CnMoV genome, ranging from 4417 to 4419 nt, encodes five ORFs. It shares 48.1% nucleotide sequence identity with cocksfoot mottle virus and 69.8% with the recently discovered Poaceae Liege sobemovirus. Phylogenetic analysis supports classification within the genus Sobemovirus. Sequenced CnMoV isolates exhibit 96.4-99.9% identity. Nucleotide substitutions leading to amino acid changes showed no host associations. However, amino acid changes in the coat protein appear to be linked to differences in serological properties. Aphid transmission tests confirmed non-transmissibility, consistent with earlier observations for the English isolate.

Turnip Mosaic Virus Transcriptional Slippage Dynamics and Distribution in RNA Subpopulations.

Potyviruses comprise the largest and most important group of plant positive-strand RNA viruses. The potyviral cell-to-cell movement protein P3N-PIPO is expressed via transcriptional slippage at a conserved GAAAAAA sequence, leading to insertion of an extra 'A' in a proportion of viral transcripts. Transcriptional slippage is determined by the potyviral replicase, the conserved slippery site, and its flanking nucleotides. Here, we investigate the dynamics of transcriptional slippage at different slip-site sequences, infection stages, and environmental conditions. We detect a modest increase in the level of transcripts with insertion towards later timepoints. In addition, we investigate the fate of transcripts with insertion by separately looking at different RNA subpopulations: (+)RNA, (-)RNA, translated RNA, and virion RNA. We find differences in insertional slippage between (+)RNA and (-)RNA but not other subpopulations. Our results suggest that there can be selection against the use of (-)RNAs with insertions as templates for transcription or replication and demonstrate that insertional slippage can occur at high frequency also during (-)RNA synthesis. Since transcripts with insertions are potential targets for degradation, we investigate the connection to nonsense-mediated decay (NMD). We find that these transcripts are targeted to NMD, but we only observe an impact on the level of transcripts with insertion when the insertional slippage rate is high. Together, these results further our understanding of the mechanism and elucidate the dynamics of potyviral transcriptional slippage. [Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

ABCE1 is essential for S phase progression in human cells.

ABCE1 is a highly conserved protein universally present in eukaryotes and archaea, which is crucial for the viability of different organisms. First identified as RNase L inhibitor, ABCE1 is currently recognized as an essential translation factor involved in several stages of eukaryotic translation and ribosome biogenesis. The nature of vital functions of ABCE1, however, remains unexplained. Here, we study the role of ABCE1 in human cell proliferation and its possible connection to translation. We show that ABCE1 depletion by siRNA results in a decreased rate of cell growth due to accumulation of cells in S phase, which is accompanied by inefficient DNA synthesis and reduced histone mRNA and protein levels. We infer that in addition to the role in general translation, ABCE1 is involved in histone biosynthesis and DNA replication and therefore is essential for normal S phase progression. In addition, we analyze whether ABCE1 is implicated in transcript-specific translation via its association with the eIF3 complex subunits known to control the synthesis of cell proliferation-related proteins. The expression levels of a few such targets regulated by eIF3A, however, were not consistently affected by ABCE1 depletion.

ABCE1 is a highly conserved RNA silencing suppressor.

ATP-binding cassette sub-family E member 1 (ABCE1) is a highly conserved protein among eukaryotes and archaea. Recent studies have identified ABCE1 as a ribosome-recycling factor important for translation termination in mammalian cells, yeast and also archaea. Here we report another conserved function of ABCE1. We have previously described AtRLI2, the homolog of ABCE1 in the plant Arabidopsis thaliana, as an endogenous suppressor of RNA silencing. In this study we show that this function is conserved: human ABCE1 is able to suppress RNA silencing in Nicotiana benthamiana plants, in mammalian HEK293 cells and in the worm Caenorhabditis elegans. Using co-immunoprecipitation and mass spectrometry, we found a number of potential ABCE1-interacting proteins that might support its function as an endogenous suppressor of RNA interference. The interactor candidates are associated with epigenetic regulation, transcription, RNA processing and mRNA surveillance. In addition, one of the identified proteins is translin, which together with its binding partner TRAX supports RNA interference.