• BMB Reports
• /
• v.42 no.4
• /
• pp.185-188
• /
• 2009

Transcripts contain introns that are usually removed from premessenger RNA (MRNA) in the process of pre-mRNA splicing. After splicing, the mature RNA is exported from the nucleus to the cytoplasm. The splicing and export processes are coupled. UAP56 protein, which is ubiquitously present in organisms from yeasts to humans, is a DExD/H-box family RNA helicase that is an essential splicing factor with various functions in the prespliceosome assembly and mature spliceosome assembly. Collective evidence indicates that UAP56 has an essential role in mRNA nuclear export. This mini-review summarizes recent evidence for the role of UAP56 in pre-mRNA splicing and nuclear export.

• Journal of Microbiology
• /
• v.41 no.2
• /
• pp.115-120
• /
• 2003

Mex67p/Tap are evolutionally conserved mRNA export factors. To identify mutations in genes that are functionally linked to mex67 with respect to mRNA export, we used a synthetic lethal genetic screen in Schizosaccharomyces pombe. Three synthetic lethal mutants were isolated and mutations in these mutants defined separate complementation groups. These mutants exhibited the accumulation of poly A$\^$+/ RNA in the nucleus, with a decrease in the cytoplasm under synthetically lethal conditions, suggesting that the mutations cause an mRNA nuclear export defect. In addition, the S. pombe genes that were found to be involved in mRNA export did not suppress the synthetic lethality of these mutants. These results indicate that the isolated mutants contain mutations in new genes, which are involved in mRNA export from the nucleus.

• Korean Journal of Microbiology
• /
• v.54 no.2
• /
• pp.91-97
• /
• 2018

The evolutionally conserved TREX complex member, Yra1/ALY, belongs to the REF (RNA and export factor binding proteins) family of hnRNP-like proteins, which has been implicated in multiple processes including transcription, nuclear RNA stability, and mRNA export. Fission yeast, Schizosaccharomyces pombe, genome encodes two members of REF proteins. In addition to Mlo3 known previously as an mRNA export factor, there is the other REF protein, Tho4, which is predicted as a component of THO complex. Here we showed that deletion of tho4 (SPBC106.12c) gene does not inhibit both growth and nuclear mRNA export. However, overexpression of tho4 displays growth retardation and slight accumulation of $poly(A)^+$ RNA in the nucleus. Neither ${\Delta}tho4$ ${\Delta}mlo3$ nor ${\Delta}tho4$ ${\Delta}mex67$ double mutants exhibit additive growth defect. Moreover, yeast two-hybrid and co-immunoprecipitation analysis did not show that the Tho4 protein interacted with any members of TREX complex and mRNA export factor Rae1. Contrary to expectation, these observations support that the S. pombe Tho4 is not a component of TREX complex, and not directly involved in bulk mRNA export from the nucleus.

• Korean Journal of Microbiology
• /
• v.51 no.4
• /
• pp.435-439
• /
• 2015

THO/TREX complex plays an important role in transcriptional elongation, mRNA processing, nuclear RNA export, and genome stability. A fission yeast, Schizosaccharomyces pombe, SPBC577.04 gene encoding the ortholog of THOC5, a component of THO/TREX complex, was identified and characterized. The S. pombe thoc5 (spthoc5) is not essential for both growth and mRNA export, but deletion of the spthoc5 gene caused growth defect and slight accumulation of $poly(A)^+$ RNA in the nucleus. And the functional spThoc5-GFP protein is localized mainly in the nucleus. Co-immunoprecipitation analysis showed that the Hpr1(THOC1) protein, an evolutionally well-conserved component of THO/TREX complex, interacted with spThoc5 as well as Tho2(THOC2), another subunit of THO complex. These results suggest that S. pombe Thoc5 as a component of THO/TREX complex is also involved in mRNA export from the nucleus.

• Molecules and Cells
• /
• v.37 no.1
• /
• pp.1-8
• /
• 2014

Mammalian-cell messenger RNAs (mRNAs) are generated in the nucleus from precursor RNAs (pre-mRNAs, which often contain one or more introns) that are complexed with an array of incompletely inventoried proteins. During their biogenesis, pre-mRNAs and their derivative mRNAs are subject to extensive cis-modifications. These modifications promote the binding of distinct polypeptides that mediate a diverse array of functions needed for mRNA metabolism, including nuclear export, inspection by the nonsense-mediated mRNA decay (NMD) quality-control machinery, and synthesis of the encoded protein product. Ribonucleoprotein complex (RNP) remodeling through the loss and gain of protein constituents before and after pre-mRNA splicing, during mRNA export, and within the cytoplasm facilitates NMD, ensuring integrity of the transcriptome. Here we review the mRNP rearrangements that culminate in detection and elimination of faulty transcripts by mammalian-cell NMD.

• BMB Reports
• /
• v.56 no.9
• /
• pp.514-519
• /
• 2023

Methyltransferase-like 3 (METTL3), a key component of the m⁶A methyltransferase complex, regulates the splicing, nuclear transport, stability, and translation of its target genes. However, the mechanism underlying the regulation of METTL3 expression by alternative splicing (AS) remains unknown. We analyzed the expression pattern of METTL3 after AS in human tissues and confirmed the expression of an isoform retaining introns 8 and 9 (METTL3-IR). We confirmed the different intracellular localizations of METTL3-IR and METTL3 proteins using immunofluorescence microscopy. Furthermore, the endogenous expression of METTL3-IR at the protein level was different from that at the mRNA level. We found that 3'-UTR generation by intron retention (IR) inhibited the export of METTL3-IR mRNA to the cytoplasm, which in turn suppressed protein expression. To the best of our knowledge, this is the first study to confirm the regulation of METTL3 gene expression by AS, providing evidence that the suppression of METTL3 protein expression by IR is an integral part of the mechanism by which 3'-UTR generation regulates protein expression via inhibition of RNA export to the cytoplasm.

• Korean Journal of Microbiology
• /
• v.53 no.1
• /
• pp.49-54
• /
• 2017

Sus1 / ENY2 is a tiny conserved protein that is involved in chromatin remodeling and mRNA biogenesis. Sus1 is associated to two nuclear complexes, the transcriptional coactivator SAGA and the nuclear pore associated TREX2. In fission yeast, Schizosaccharomyces pombe, ortholog of Sus1 / ENY2 was identified from the genome database. Tetrad analysis showed that the S. pombe sus1 is not essential for growth. However, deletion of the sus1 gene caused cold-sensitive growth retardation with slight accumulation of $poly(A)^+$ RNA in the nucleus. And the Sus1-GFP protein is localized mainly in the nucleus. Yeast two-hybrid analysis and co-immunoprecipitation experiment showed that Sus1 interacts with Sac3, another subunit of TREX2 complex. These results suggest that S. pombe Sus1 is also involved in mRNA export from the nucleus as a component of TREX-2 complex.

• Journal of Life Science
• /
• v.23 no.11
• /
• pp.1311-1316
• /
• 2013

Heterogeneous nuclear ribonucleoprotein L (hnRNP L) is a major pre-mRNA binding protein and it is an abundant nuclear protein that shuttles between the nucleus and the cytoplasm. hnRNP L is known to be related to many cellular processes, including chromatin modification, pre-mRNA splicing, mRNA export of intronless genes, internal ribosomal entry site (IRES)-mediated translation, mRNA stability, and spermatogenesis. In order to identify the cellular proteins interacting with hnRNP L, this study performed a yeast two-hybrid screening, using a human liver cDNA library. The study identified insulin-like growth factor binding protein-4 (IGFBP-4) as a novel interaction partner of hnRNP L in the human liver. It then discovered, for the first time, that hnRNP L interacts specifically with IGFBP-4 in a yeast two-hybrid system. The authenticity of this two-hybrid interaction of hnRNP L and IGFBP-4 was confirmed by an in vitro pull-down assay.

• Journal of Life Science
• /
• v.7 no.3
• /
• pp.161-166
• /
• 1997

HIV-1 Rev protein plays an important role in regulating the expression of viral structural proteins. It allows the nuclear export and accumulation of unspliced and partially spliced viral mRNA in the cytoplasm. The Rev-responsive element RNA, present in the env gene, forms a higly ordered RNA secondary structure and is required for the Rev-mediated mRNA export. For this process to complete factor(s) are strongly suggested. From our experiments of electrophoretic mobility shift, UV-crosslinking and SDS/PAGE, RRE RNA was found to be recognized to several nuclear factors such as 36/37, 56, 41. 76, 150 kD proteins in the order of reactivity. Among them, 36/37 and 56 kD proteins are more reactive upon a brief UV treatment (5 min) and more persistent in the presence of high amount of nonspecific competitor, heparin. Certain nuclear protein9s) seemed to recognize the RRE RNA structure in competition with Rev to gel mobility shift assay.

• Korean Journal of Microbiology
• /
• v.53 no.4
• /
• pp.292-296
• /
• 2017

In eukaryote, THO/TREX complex plays a critical role in transcriptional elongation, pre-mRNA processing, and nuclear mRNA export. This complex is evolutionally well- conserved, but there are some differences in composition and function according to organisms. Here we showed that spTex1, a component of THO/TREX complex, is not essential for growth and mRNA export in a fission yeast, Schizosaccharomyces pombe, which is more similar to higher eukaryote than budding yeast. Deletion and overexpression of the spTex1 gene do not lead to any detectable growth phenotype and accumulation of poly(A)+ RNA in the nucleus. And the spTex1-GFP protein is localized mainly in the nucleus. Yeast two-hybrid and Co-immunoprecipitation analysis showed that the spTex1 protein interacted with spHpr1 (THOC1) and spTho2 (THOC2), main subunits of THO complex. We conclude that the S. pombe Tex1 is a component of THO/TREX complex, but does not plays important roles in growth and bulk mRNA export from the nucleus.