Identification of a Human Endonuclease Complex Reveals a Link between tRNA Splicing and Pre-mRNA 3′ End Formation

PTC Therapeutics, 100 Corporate Court, South Plainfield, NJ 07080, USA.
Cell (Impact Factor: 32.24). 05/2004; 117(3):311-21. DOI: 10.1016/S0092-8674(04)00342-3
Source: PubMed


tRNA splicing is a fundamental process required for cell growth and division. The first step in tRNA splicing is the removal of introns catalyzed in yeast by the tRNA splicing endonuclease. The enzyme responsible for intron removal in mammalian cells is unknown. We present the identification and characterization of the human tRNA splicing endonuclease. This enzyme consists of HsSen2, HsSen34, HsSen15, and HsSen54, homologs of the yeast tRNA endonuclease subunits. Additionally, we identified an alternatively spliced isoform of SEN2 that is part of a complex with unique RNA endonuclease activity. Surprisingly, both human endonuclease complexes are associated with pre-mRNA 3' end processing factors. Furthermore, siRNA-mediated depletion of SEN2 exhibited defects in maturation of both pre-tRNA and pre-mRNA. These findings demonstrate a link between pre-tRNA splicing and pre-mRNA 3' end formation, suggesting that the endonuclease subunits function in multiple RNA-processing events.

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    • "During their nuclear biogenesis, pre-tRNAs undergo various maturation steps including cleavage of the 5′ leader sequence by RNase P, RNase Z-dependent 3′ end processing, 3′ CCA addition and introduction of a myriad of nucleotide modifications (reviewed in Ref. [24]). Interestingly, in yeast, splicing of intron-containing tRNAs takes place on the mitochondrial outer surface [25] [26], whereas in mammalian cells, the tRNA splicing machinery is located within the nucleus [27] and intron removal takes place prior to export through the NPC. The major export receptor for tRNAs, which is specific for this class of RNAs, is Los1 in yeast (EXP-t/ XpoT in mammals) [28] [29] [30] and translocation follows the general paradigm for Ran-dependent transport (Fig. 2a). "
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    ABSTRACT: RNAs and ribonucleoprotein complexes (RNPs) play key roles in mediating and regulating gene expression. In eukaryotes, most RNAs are transcribed, processed and assembled with proteins in the nucleus and then either function in the cytoplasm or also undergo a cytoplasmic phase in their biogenesis. This compartmentalisation ensures that sequential steps in gene expression and RNP production are performed in the correct order and allows important quality control mechanisms that prevent the involvement of aberrant RNAs/RNPs in these cellular pathways. The selective exchange of RNAs/RNPs between the nucleus and cytoplasm is enabled by nuclear pore complexes (NPCs), which function as gateways between these compartments. RNA/RNP transport is facilitated by a range of nuclear transport receptors and adaptors, which are specifically recruited to their cargos and mediate interactions with nucleoporins to allow directional translocation through NPCs. While some transport factors are only responsible for the export/import of a certain class of RNA/RNP, others are multifunctional and, in the case of large RNPs, several export factors appear to work together to bring about export. Recent structural studies have revealed aspects of the mechanisms employed by transport receptors to enable specific cargo recognition, and genome-wide approaches have provided the first insights into the diverse composition of pre-mRNPs during export. Furthermore, the regulation of RNA/RNP export is emerging as an important means to modulate gene expression in stress conditions and disease.
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    • "ELAC2 was suggested to be involved in nuclear and mitochondrial tRNA 3 ′ end processing in vivo, whereas the cellular role of ELAC1 remains unclear (Rossmanith 2011). A subset of pre-tRNAs contains introns that are removed during nuclear tRNA splicing reactions in mammals (Paushkin et al. 2004). Prior to export to the cytoplasm, the nucleotidyltransferase Trnt1 adds a nontemplated CCA trinucleotide to the 3 ′ end of the tRNA that acts as a prerequisite for aminoacylation (Reichert et al. 2001). "
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    No preview · Article · Jul 2015 · RNA
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    • "There is appreciable conservation among these eukaryotic Sen2 and Sen34 subunits, and archaeal endonucleases, indicating the same evolutional origin of splicing machinery. The human Sen complex also contains Clp1 (hClp1) (Paushkin et al., 2004; Weitzer and Martinez, 2007). Clp1 was first identified as a component of the cleavage factor II for polyadenylation of pre-mRNAs (de Vries et al., 2000), and then re-identified as an in vitro kinase for tRNA exons when searching for an enzyme phosphorylating siRNAs displaying a 5′-OH group (Figure 4) (Weitzer and Martinez, 2007). "
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