The degree of conservation and evolution of cytoplasmic mRNA metabolism pathways across the eukaryotes remains incompletely resolved. In this study, we describe a comprehensive genome and transcriptome-wide analysis of proteins involved in mRNA maturation, translation, and mRNA decay across representative organisms from the six eukaryotic super-groups. We demonstrate that eukaryotes share commo...

The major-histocompatibility-complex protein UAP56 (BAT1) is a DEAD-box helicase that is deposited on mRNA during splicing. UAP56 is retained on spliced mRNA in an exon junction complex (EJC) or, alternatively, with the TREX complex at the 5' end, where it might facilitate the export of the spliced mRNA to the cytoplasm. Using confocal microscopy, UAP56 was found to be concentrated in RNA-splic...

The human Upf (hUpf) proteins work at the core of the nonsense-mediated mRNA decay (NMD) pathway. The three hUpf proteins, hUpf1, hUpf2 and hUpf3, form the hUpf complex, which is critical for the recognition and degradation of mRNAs containing premature termination codons (PTCs). The recognition of PTC-containing mRNAs by the hUpf complex in mammalian cells is promoted by the splicing dependent...

The nonsense-mediated mRNA decay (NMD) pathway rids eukaryotic cells of mRNAs with premature termination codons. There is contradictory evidence as to whether mammalian NMD is a nuclear or a cytoplasmic process. Here, we show evidence that NMD in human cells occurs primarily, if not entirely, in the cytoplasm. Polypeptides designed to inhibit interactions between NMD factors specifically impede...

Nonsense-mediated mRNA decay (NMD), which degrades transcripts harboring a premature termination codon (PTC), depends on the helicase up-frameshift 1 (UPF1). However, mRNAs that are not NMD targets also bind UPF1. What governs the timing, position, and function of UPF1 binding to mRNAs remains unclear. We provide evidence that (i) multiple UPF1 molecules accumulate on the 3'-untranslated region...

Nonsense-mediated mRNA decay (NMD) is essential for removing premature termination codon-containing transcripts from cells. Studying the NMD pathway in model organisms can help to elucidate the NMD mechanism in humans and improve our understanding of how this biologically important process has evolved. Ciliates are among the earliest branching eukaryotes; their NMD mechanism is poorly understoo...

PIWI-interacting RNAs (piRNAs) are effectors of transposable element (TE) silencing in the reproductive apparatus. In Drosophila ovarian somatic cells, piRNAs arise from longer single-stranded RNA precursors that are processed in the cytoplasm presumably within the Yb-bodies. piRNA precursors encoded by the flamenco (flam) piRNA cluster accumulate in a single focus away from their sites of tran...

Arc is a unique immediate early gene whose expression is induced as synapses are being modified during learning. The uniqueness comes from the fact that newly synthesized Arc mRNA is rapidly transported throughout dendrites where it localizes near synapses that were recently activated. Here, we summarize aspects of Arc mRNA translation in dendrites in vivo, focusing especially on features of it...

mRNA localization by active transport is a regulated process that requires association of mRNPs with protein motors for transport along either the microtubule or the actin cytoskeleton. oskar mRNA localization at the posterior pole of the Drosophila oocyte requires a specific mRNA sequence, termed the SOLE, which comprises nucleotides of both exon 1 and exon 2 and is assembled upon splicing. Th...

Spliceostatin A, meayamycin, and pladienolide B are small molecules that target the SF3b subunit of spliceosomal U2 snRNP. These compounds are attracting much attention as tools to manipulate splicing and potential anti-cancer drugs. We investigated the effects of these inhibitors on mRNA transport and stability in human cells. Upon splicing inhibition unspliced pre-mRNAs accumulated in the nuc...