scholarly journals Translation of Polioviral mRNA Is Inhibited by Cleavage of Polypyrimidine Tract-Binding Proteins Executed by Polioviral 3Cpro

2002 ◽  
Vol 76 (5) ◽  
pp. 2529-2542 ◽  
Author(s):  
Sung Hoon Back ◽  
Yoon Ki Kim ◽  
Woo Jae Kim ◽  
Sungchan Cho ◽  
Hoe Rang Oh ◽  
...  
Keyword(s):  
Binding Proteins ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Binding Protein ◽  
Internal Ribosomal Entry Site ◽  
Polypyrimidine Tract ◽  
Entry Site ◽  
Polypyrimidine Tract Binding ◽  
Polypyrimidine Tract Binding Protein ◽  
Target Sites

ABSTRACT The translation of polioviral mRNA occurs through an internal ribosomal entry site (IRES). Several RNA-binding proteins, such as polypyrimidine tract-binding protein (PTB) and poly(rC)-binding protein (PCBP), are required for the poliovirus IRES-dependent translation. Here we report that a poliovirus protein, 3Cpro (and/or 3CDpro), cleaves PTB isoforms (PTB1, PTB2, and PTB4). Three 3Cpro target sites (one major target site and two minor target sites) exist in PTBs. PTB fragments generated by poliovirus infection are redistributed to the cytoplasm from the nucleus, where most of the intact PTBs are localized. Moreover, these PTB fragments inhibit polioviral IRES-dependent translation in a cell-based assay system. We speculate that the proteolytic cleavage of PTBs may contribute to the molecular switching from translation to replication of polioviral RNA.

scholarly journals Protein Factor Requirements of the Apaf-1 Internal Ribosome Entry Segment: Roles of Polypyrimidine Tract Binding Protein and upstream of N-ras

2001 ◽  
Vol 21 (10) ◽  
pp. 3364-3374 ◽  
Author(s):  
Sally A. Mitchell ◽  
Emma C. Brown ◽  
Mark J. Coldwell ◽  
Richard J. Jackson ◽  
Anne E. Willis
Keyword(s):  
Binding Proteins ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Binding Protein ◽  
Cell Types ◽  
Polypyrimidine Tract ◽  
Internal Ribosome Entry ◽  
Polypyrimidine Tract Binding ◽  
Polypyrimidine Tract Binding Protein ◽  
Different Cell Types

ABSTRACT It has been reported previously that the 5′ untranslated region of the mRNA encoding Apaf-1 (apoptotic protease-activating factor 1) has an internal ribosome entry site (IRES), whose activity varies widely among different cell types. Here it is shown that the Apaf-1 IRES is active in rabbit reticulocyte lysates, provided that the system is supplemented with polypyrimidine tract binding protein (PTB) and upstream of N-ras (unr), two cellular RNA binding proteins previously identified to be required for rhinovirus IRES activity. In UV cross-linking assays and electrophoretic mobility shift assays with individual recombinant proteins, the Apaf-1 IRES binds unr but not PTB; however, PTB binding occurs if unr is present. Over a range of different cell types there is a broad correlation between the activity of the Apaf-1 IRES and their content of PTB and unr. In cell lines deficient in these proteins, overexpression of PTB and unr stimulated Apaf-1 IRES function. This is the first example where an IRES in a cellular mRNA has been shown to be functionally dependent, both in vitro and in vivo, on specific cellular RNA binding proteins. Given the critical role of Apaf-1 in apoptosis, these results have important implications for the control of the apoptotic cascade.

scholarly journals La protein is required for efficient translation driven by encephalomyocarditis virus internal ribosomal entry site

1999 ◽  
Vol 80 (12) ◽  
pp. 3159-3166 ◽  
Author(s):  
Yoon Ki Kim ◽  
Sung Key Jang
Keyword(s):  
Binding Proteins ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Protein A ◽  
Internal Ribosomal Entry Site ◽  
Encephalomyocarditis Virus ◽  
Entry Site ◽  
Polypyrimidine Tract Binding Protein ◽  
La Protein ◽  
Ribosomal Entry

Translation of internal ribosomal entry site (IRES)-dependent mRNAs is mediated by RNA-binding proteins as well as canonical translation factors. In order to elucidate the roles of RNA-binding proteins in IRES-dependent translation, the role of polypyrimidine tract-binding protein (PTB) and La protein in encephalomyocarditis virus (EMCV) IRES-dependent translation was investigated. PTB was required for efficient EMCV IRES-driven translation but, intriguingly, an excess of PTB suppressed it. Such a translational suppression by surplus PTB was relieved by addition of La protein. A possible role for La protein in IRES-dependent translation is discussed.

scholarly journals Polypyrimidine Tract-Binding Protein Enhances the Internal Ribosomal Entry Site-Dependent Translation of p27Kip1 mRNA and Modulates Transition from G1 to S Phase

2005 ◽  
Vol 25 (4) ◽  
pp. 1283-1297 ◽  
Author(s):  
Sungchan Cho ◽  
Jong Heon Kim ◽  
Sung Hoon Back ◽  
Sung Key Jang
Keyword(s):  
Cell Cycle ◽  
Binding Protein ◽  
Internal Ribosomal Entry Site ◽  
In Vitro Translation ◽  
Polypyrimidine Tract ◽  
Entry Site ◽  
Hl60 Cells ◽  
Polypyrimidine Tract Binding ◽  
Polypyrimidine Tract Binding Protein ◽  
Ribosomal Entry

ABSTRACT The p27Kip1 protein plays a critical role in the regulation of cell proliferation through the inhibition of cyclin-dependent kinase activity. Translation of p27Kip1 is directed by an internal ribosomal entry site (IRES) in the 5′ nontranslated region of p27Kip1 mRNA. Here, we report that polypyrimidine tract-binding protein (PTB) specifically enhances the IRES activity of p27Kip1 mRNA through an interaction with the IRES element. We found that addition of PTB to an in vitro translation system and overexpression of PTB in 293T cells augmented the IRES activity of p27Kip1 mRNA but that knockdown of PTB by introduction of PTB-specific small interfering RNAs (siRNAs) diminished the IRES activity of p27Kip1 mRNA. Moreover, the G1 phase in the cell cycle (which is maintained in part by p27Kip1) was shortened in cells depleted of PTB by siRNA knockdown. 12-O-Tetradecanoylphorbol-13-acetate (TPA)-induced differentiation in HL60 cells was used to examine PTB-induced modulation of p27Kip1 protein synthesis during differentiation. The IRES activity of p27Kip1 mRNA in HL60 cells was increased by TPA treatment (with a concomitant increase in PTB protein levels), but the levels of p27Kip1 mRNA remained unchanged. Together, these data suggest that PTB modulates cell cycle and differentiation, at least in part, by enhancing the IRES activity of p27Kip1 mRNA.

scholarly journals Determination of functional domains in polypyrimidine-tract-binding protein

1998 ◽  
Vol 331 (1) ◽  
pp. 169-175 ◽  
Author(s):  
Young L. OH ◽  
Bumsuk HAHM ◽  
Yoon K. KIM ◽  
Hae K. LEE ◽  
Joo W. LEE ◽  
...  
Keyword(s):  
Amino Acids ◽  
Rna Binding ◽  
Binding Protein ◽  
Biochemical Properties ◽  
Polypyrimidine Tract ◽  
Terminal Part ◽  
Entry Site ◽  
Cytoplasmic Factor ◽  
Polypyrimidine Tract Binding ◽  
Polypyrimidine Tract Binding Protein

Polypyrimidine-tract-binding protein (PTB) is involved in pre-mRNA splicing and internal-ribosomal-entry-site-dependent translation. The biochemical properties of various segments of PTB were analysed in order to understand the molecular basis of the PTB functions. The protein exists in oligomeric as well as monomeric form. The central part of PTB (amino acids 169–293) plays a major role in the oligomerization. PTB contains several RNA-binding motifs. Among them, the C-terminal part of PTB (amino acids 329–530) exhibited the strongest RNA-binding activity. The N-terminal part of PTB is responsible for the enhancement of RNA binding by HeLa cell cytoplasmic factor(s).

scholarly journals Nucleocytoplasmic Shuttling of Polypyrimidine Tract-binding Protein Is Uncoupled from RNA Export

2001 ◽  
Vol 12 (12) ◽  
pp. 3808-3820 ◽  
Author(s):  
Rajesh V. Kamath ◽  
Daniel J. Leary ◽  
Sui Huang
Keyword(s):  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Rna Binding ◽  
Binding Protein ◽  
Dependent Manner ◽  
Polypyrimidine Tract ◽  
Nucleocytoplasmic Shuttling ◽  
Polypyrimidine Tract Binding ◽  
Polypyrimidine Tract Binding Protein ◽  
Rna Export

Polypyrimidine tract binding protein, PTB/hnRNP I, is involved in pre-mRNA processing in the nucleus and RNA localization and translation in the cytoplasm. In this report, we demonstrate that PTB shuttles between the nucleus and cytoplasm in an energy-dependent manner. Deletion mutagenesis demonstrated that a minimum of the N terminus and RNA recognition motifs (RRMs) 1 and 2 are necessary for nucleocytoplasmic shuttling. Deletion of RRM3 and 4, domains that are primarily responsible for RNA binding, accelerated the nucleocytoplasmic shuttling of PTB. Inhibition of transcription directed by either RNA polymerase II alone or all RNA polymerases yielded similar results. In contrast, selective inhibition of RNA polymerase I did not influence the shuttling kinetics of PTB. Furthermore, the intranuclear mobility of GFP-PTB, as measured by fluorescence recovery after photobleaching analyses, increased significantly in transcriptionally inactive cells compared with transcriptionally active cells. These observations demonstrate that nuclear RNA transcription and export are not necessary for the shuttling of PTB. In addition, binding to nascent RNAs transcribed by RNA polymerase II and/or III retards both the nuclear export and nucleoplasmic movement of PTB. The uncoupling of PTB shuttling and RNA export suggests that the nucleocytoplasmic shuttling of PTB may also play a regulatory role for its functions in the nucleus and cytoplasm.

Polypyrimidine-tract-binding protein: a multifunctional RNA-binding protein

2008 ◽  
Vol 36 (4) ◽  
pp. 641-647 ◽  
Author(s):  
Kirsty Sawicka ◽  
Martin Bushell ◽  
Keith A. Spriggs ◽  
Anne E. Willis
Keyword(s):  
Translation Initiation ◽  
Cellular Localization ◽  
Rna Binding ◽  
Binding Protein ◽  
Control Cell ◽  
Rna Binding Protein ◽  
Alternative Form ◽  
Polypyrimidine Tract ◽  
Polypyrimidine Tract Binding ◽  
Polypyrimidine Tract Binding Protein

PTB (polypyrimidine-tract-binding protein) is a ubiquitous RNA-binding protein. It was originally identified as a protein with a role in splicing but it is now known to function in a large number of diverse cellular processes including polyadenylation, mRNA stability and translation initiation. Specificity of PTB function is achieved by a combination of changes in the cellular localization of this protein (its ability to shuttle from the nucleus to the cytoplasm is tightly controlled) and its interaction with additional proteins. These differences in location and trans-acting factor requirements account for the fact that PTB acts both as a suppressor of splicing and an activator of translation. In the latter case, the role of PTB in translation has been studied extensively and it appears that this protein is required for an alternative form of translation initiation that is mediated by a large RNA structural element termed an IRES (internal ribosome entry site) that allows the synthesis of picornaviral proteins and cellular proteins that function to control cell growth and cell death. In the present review, we discuss how PTB regulates these disparate processes.

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