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

• The Korean Journal of Physiology and Pharmacology
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• v.14 no.1
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• pp.15-20
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• 2010

It has been shown that CA repeats in the 3'-untranslated region (UTR) of bcl-2 mRNA contribute the constitutive decay of bcl-2 mRNA and that hnRNP L (heterogenous nuclear ribonucleoprotein L) interacts with CA repeats in the 3'-UTR of bcl-2 mRNA, both in vitro and in vivo. The aim of this study was to determine whether the alteration of hnRNP L affects the stability of bcl-2 mRNA in vivo. Human breast carcinoma MCF-7 cells were transfected with hnRNP L-specific shRNA or hnRNP L-expressing vector to decrease or increase hnRNP L levels, respectively, followed by an actinomycin D chase. An RT-PCR analysis showed that the rate of degradation of endogenous bcl-2 mRNA was not affected by the decrease or increase in the hnRNP L levels. Furthermore, during apoptosis or autophagy, in which bcl-2 expression has been reported to decrease, no difference in the degradation of bcl-2 mRNA was observed between control and hnRNP L-knock down MCF-7 Cells. On the other hand, the levels of AUF-1 and nucleolin, transacting factors for ARE in the 3'UTR of bcl-2 mRNA, were not significantly affected by the decrease in hnRNP L, suggesting that a disturbance in the quantitative balance between these transacting factors is not likely to interfere with the effect of hnRNP L. Collectively, the findings indicate that the decay of bcl-2 mRNA does not appear to be directly controlled by hnRNP L in vivo.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.575-580
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• 2017

This study analyzed the effects of RGG box of hnRNP A1 on its subcellular localization and stabilization of hnRNP A1 over a three year period from October 2014. First, a 6R/K mutation in RGG box was generated, and pcDNA1-HA-hnRNP A1(6R/K) was constructed. The subcellular localization of hnRNP A1(6R/K) from the HeLa cells transfected with this plasmid DNA was analyzed by immunofluorescence microscopy. HA-hnRNP A1(6R/K) was found to exhibit nuclear and cytoplasmic fluorescence. The stability of hnRNP A1(6R/K) was checked by Western blot analysis using the expressed protein from the HeLa cells transfected with the pcDNA1-HA-hnRNP A1(6R/K). The results show that HA-hnRNP A1(6R/K) has a smaller size. These confirm that HA-hnRNP A1(6R/K) is localized both in the nuclear and cytoplasm, not because 6R/K mutation affects the nuclear localization of hnRNP A1, but because 6R/K mutation causes hnRNP A1(6R/K) to cleave at the mutation or near the mutation site. The cleaved protein fragment, which lacks the M9 domain (i.e. nuclear localization signal of hnRNP A1), did not exhibit nuclear fluorescence. This suggests that the arginines of RGG box in hnRNP A1 play an important role in stabilizing hnRNP A1. An analysis of the RNA-binding ability of hnRNP A1(6R/K) expressed and purified from bacteria will be a subsequent research project.

• Bulletin of the Korean Chemical Society
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• v.30 no.4
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• pp.791-793
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• 2009

Escherichia coli RNase P is composed of a large RNA subunit (M1 RNA) and a small protein subunit (C5 protein). Since both subunits are assembled in a 1:1 ratio, expression of M1 RNA and C5 protein should be coordinately regulated for RNase P to be efficiently synthesized in the cell. However, it is not known yet how the coordination occurs. In this study, we investigated how overexpression of C5 protein affects expression of the rnpB gene encoding M1 RNA, using a lysogenic strain, which carries an rnpB-lacZ transcription fusion. Primer extension analysis of rnpB-lacZ fusion transcripts showed that the overexpression of C5 protein increased the amount of the fusion transcripts, suggesting that rnpB expression increases with the increase of intracellular level of C5 protein.

• Animal cells and systems
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• v.12 no.3
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• pp.143-148
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• 2008

Heterogeneous nuclear ribonucleoprotein E1(hnRNP E1) is one of the primary pre-mRNA binding proteins in human cells. It consists of 356 amino acid residues and harbors three hnRNP K homology(KH) domains that mediate RNA-binding. The hnRNP E1 protein was shown to play important roles in mRNA stabilization and translational control. In order to enhance our understanding of the cellular functions of hnRNP E1, we searched for interacting proteins through a yeast two-hybrid screening while using HeLa cDNA library as target. One of the cDNA clones was found to be human ribosomal protein L18a cDNA(GenBank accession number BC071920). We demonstrated in this study that human ribosomal protein L18a, a constituent of ribosomal protein large subunit, interacts specifically with hnRNP E1 in the yeast two-hybrid system. Such an interaction was observed for the first time in this study, and was also verified by biochemical assay.

• Bulletin of the Korean Chemical Society
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• v.28 no.6
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• pp.1010-1014
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• 2007

M1 RNA is the catalytic component of RNase P, a tRNA-processing enzyme in Escherichia coli. M1 RNA is produced in the cell by transcription of the rnpB gene and subsequent processing at the 3' end. The 3' flanking region of rnpB contains repeated sets of overlapping sequences coding for small proteins. The issue of whether these proteins are expressed remains to be established. In this study, we showed the expression of a small protein encoded by the first repeat within the 3' flanking region of rnpB. Interestingly, protein expression was increased at lower temperatures. The termination efficiency of rnpB terminators was decreased at lower temperatures, suggesting that antitermination is responsible for enhanced protein expression. Moreover, the purified small protein contained M1 RNA, implying a role as a specific RNA-binding protein.

• BMB Reports
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• v.52 no.11
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• pp.641-646
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• 2019

The Ron proto-oncogene is a human receptor for macrophage-stimulating protein (MSP). The exclusion of exon 11 in alternative splicing generates ${\Delta}RON$ protein that is constitutively activated. Heterogenous ribonucleaoprotein (hnRNP) $C_1/C_2$ is one of the most abundant proteins in cells. In this manuscript, we showed that both hnRNP $C_1$ and $C_2$ promoted exon 11 inclusion of Ron pre-mRNA and that hnRNP $C_1$ and hnRNP $C_2$ functioned independently but not cooperatively. Moreover, hnRNP $C_1$ stimulated exon 11 splicing through intron 10 activation but not through intron 11 splicing. Furthermore, we showed that, whereas the RRM domain was required for hnRNP $C_1$ function, the Asp/Glu domain was not. In conclusion, hnRNP $C_1/C_2$ promoted exon 11 splicing independently by stimulating intron 10 splicing through RRM but not through the Asp/Glu domain.

• Molecules and Cells
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• v.19 no.2
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• pp.239-245
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• 2005

Factor for inversion stimulation (FIS), the Escherichia coli protein, is a positive regulator of the transcription of genes that encode stable RNA species, such as rRNA and tRNA. Transcription of the rnpB gene encoding M1 RNA, the catalytic subunit of E. coli RNase P, rapidly declines under stringent conditions, as does that of other stable RNAs. There are multiple putative FIS binding sites upstream of the rnpB promoter. We tested whether FIS binds to these sites, and if so, how it affects rnpB transcription. In vitro binding assays revealed specific binding of FIS to multiple sites in the rnpB promoter region. Interestingly, FIS bound not only to the upstream region of the promoter, but also to the region from +4 to +18. FIS activated rnpB transcription in vitro, but the level of activation was much lower than that of the rrnB promoter for rRNA. We also examined the effects of FIS on rnpB transcription in vivo using isogenic $fis^+$ and $fis^-$ strains. rnpB transcription was higher in the $fis^-$ than the $fis^+$ cells during the transitions from lag to exponential phase, and from exponential to stationary phase.

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

• Journal of the Korean Chemical Society
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• v.52 no.5
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• pp.580-582
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• 2008