scholarly journals ARF Function Does Not Require p53 Stabilization or Mdm2 Relocalization

2002 ◽  
Vol 22 (1) ◽  
pp. 196-206 ◽  
Author(s):  
Chandrashekhar Korgaonkar ◽  
Lili Zhao ◽  
Modestos Modestou ◽  
Dawn E. Quelle
Keyword(s):  
Transcriptional Activation ◽  
Growth Arrest ◽  
Nucleolar Localization ◽  
Wild Type ◽  
Growth Inhibitory ◽  
Nucleolar Localization Signal ◽  
Localization Signal ◽  
Reporter Assays ◽  
Dependent Growth ◽  
Block Growth

ABSTRACT It is generally accepted that the ARF tumor suppressor induces p53-dependent growth arrest by sequestering the p53 antagonist Mdm2 in the nucleolus. Previous mutagenic studies of murine ARF suggested that residues 1 through 14 and 26 through 37 were critical for Mdm2 binding, while the latter domain also governed ARF nucleolar localization. We show that mouse ARF residues 6 to 10 and 21 to 25 are required for ARF-induced growth arrest whereas residues 1 to 5 and 29 to 34 are dispensable. Deletion of the putative nucleolar localization signal 31RRPR34 did not prevent nucleolar localization. Surprisingly, unlike wild-type ARF, growth-inhibitory mutants D1-5 and D29-34 failed to stabilize p53 yet induced its transcriptional activation in reporter assays. This suggests that p53 stabilization is not essential for ARF-mediated activation of p53. Like wild-type ARF, both mutants also exhibited p53-independent function since they were able to arrest p53/Mdm2-null cells. Notably, other mutants lacking conserved residues 6 to 10 or 21 to 25 were unable to suppress growth in p53-positive cells despite nucleolar localization and the ability to import Mdm2. Those observations stood in apparent contrast to the ability of wild-type ARF to block growth in some cells without relocalizing endogenous Mdm2 to nucleoli. Together, these data show a lack of correlation between ARF activity and Mdm2 relocalization, suggesting that additional events other than Mdm2 import are required for ARF function.

scholarly journals Modulation of p53-mediated transcriptional repression and apoptosis by the adenovirus E1B 19K protein.

1995 ◽  
Vol 15 (2) ◽  
pp. 1060-1070 ◽  
Author(s):  
P Sabbatini ◽  
S K Chiou ◽  
L Rao ◽  
E White
Keyword(s):  
Transcriptional Activation ◽  
Transcriptional Repression ◽  
Growth Arrest ◽  
Temperature Sensitive ◽  
Wild Type ◽  
Dna Virus ◽  
Adenovirus E1a ◽  
Reporter Assays ◽  
Adenovirus E1b ◽  
Transforming Proteins

BRK cell lines that stably express adenovirus E1A and a murine temperature-sensitive p53 undergo apoptosis when p53 assumes the wild-type conformation. Expression of the E1B 19,000-molecular-weight (19K) protein rescues cells from this p53-mediated apoptosis and diverts cells to a growth-arrested state. As p53 likely functions as a tumor suppressor by regulating transcription, the ability of the E1B 19K protein to regulate p53-mediated transactivation and transcriptional repression was investigated. In promoter-reporter assays the E1B 19K did not block p53-mediated transactivation but did alleviate p53-mediated transcriptional repression. E1B 19K expression permitted efficient transcriptional activation of the p21/WAF-1/cip-1 mRNA by p53, consistent with maintenance of the growth arrest function of p53. The E1B 19K protein is thereby unique among DNA virus-transforming proteins that target p53 for inactivation in that it selectively modulates the transcriptional properties of p53. The E1B 19K protein also rescued cells from apoptosis induced by inhibitors of transcription and protein synthesis. This suggests that cell death may result from the inhibition of expression of survival factors which function to maintain cell viability. p53 may induce apoptosis through generalized transcriptional repression. In turn, the E1B 19K protein may prevent p53-mediated apoptosis by alleviating p53-mediated transcriptional repression.

scholarly journals NOA36 Protein Contains a Highly Conserved Nucleolar Localization Signal Capable of Directing Functional Proteins to the Nucleolus, in Mammalian Cells

PLoS ONE ◽  
2013 ◽  
Vol 8 (3) ◽  
pp. e59065 ◽  
Author(s):  
Ivan S. de Melo ◽  
Maria D. Jimenez-Nuñez ◽  
Concepción Iglesias ◽  
Antonio Campos-Caro ◽  
David Moreno-Sanchez ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Nucleolar Localization ◽  
Nucleolar Localization Signal ◽  
Localization Signal

scholarly journals Nonstructural Protein NSs of Schmallenberg Virus Is Targeted to the Nucleolus and Induces Nucleolar Disorganization

2016 ◽  
Vol 91 (1) ◽  
Author(s):  
Julie Gouzil ◽  
Aurore Fablet ◽  
Estelle Lara ◽  
Grégory Caignard ◽  
Marielle Cochet ◽  
...  
Keyword(s):  
Rna Polymerase Ii ◽  
Virulence Factor ◽  
Nonstructural Protein ◽  
Schmallenberg Virus ◽  
Nucleolar Localization ◽  
Pol Ii ◽  
Nucleolar Localization Signal ◽  
Localization Signal ◽  
Infected Cells ◽  
Cellular Transcription

ABSTRACT Schmallenberg virus (SBV) was discovered in Germany in late 2011 and then spread rapidly to many European countries. SBV is an orthobunyavirus that causes abortion and congenital abnormalities in ruminants. A virus-encoded nonstructural protein, termed NSs, is a major virulence factor of SBV, and it is known to promote the degradation of Rpb1, a subunit of the RNA polymerase II (Pol II) complex, and therefore hampers global cellular transcription. In this study, we found that NSs is mainly localized in the nucleus of infected cells and specifically appears to target the nucleolus through a nucleolar localization signal (NoLS) localized between residues 33 and 51 of the protein. NSs colocalizes with nucleolar markers such as B23 (nucleophosmin) and fibrillarin. We observed that in SBV-infected cells, B23 undergoes a nucleolus-to-nucleoplasm redistribution, evocative of virus-induced nucleolar disruption. In contrast, the nucleolar pattern of B23 was unchanged upon infection with an SBV recombinant mutant with NSs lacking the NoLS motif (SBVΔNoLS). Interestingly, unlike wild-type SBV, the inhibitory activity of SBVΔNoLS toward RNA Pol II transcription is impaired. Overall, our results suggest that a putative link exists between NSs-induced nucleolar disruption and its inhibitory function on cellular transcription, which consequently precludes the cellular antiviral response and/or induces cell death. IMPORTANCE Schmallenberg virus (SBV) is an emerging arbovirus of ruminants that spread in Europe between 2011 and 2013. SBV induces fetal abnormalities during gestation, with the central nervous system being one of the most affected organs. The virus-encoded NSs protein acts as a virulence factor by impairing host cell transcription. Here, we show that NSs contains a nucleolar localization signal (NoLS) and induces disorganization of the nucleolus. The NoLS motif in the SBV NSs is absolutely necessary for virus-induced inhibition of cellular transcription. To our knowledge, this is the first report of nucleolar functions for NSs within the Bunyaviridae family.

scholarly journals Internal Modification of U2 Small Nuclear (Snrna) Occurs in Nucleoli of Xenopus Oocytes

2001 ◽  
Vol 152 (6) ◽  
pp. 1279-1288 ◽  
Author(s):  
Yi-Tao Yu ◽  
Mei-Di Shu ◽  
Aarthi Narayanan ◽  
Rebecca M. Terns ◽  
Michael P. Terns ◽  
...  
Keyword(s):  
Binding Site ◽  
Xenopus Oocytes ◽  
Cajal Bodies ◽  
Nucleolar Localization ◽  
Small Nucleolar Rnas ◽  
Modified Nucleotides ◽  
Nucleolar Localization Signal ◽  
Localization Analysis ◽  
Localization Signal ◽  
Nucleolar Rnas

U2 small nuclear (sn)RNA contains a large number of posttranscriptionally modified nucleotides, including a 5′ trimethylated guanosine cap, 13 pseudouridines, and 10 2′-O-methylated residues. Using Xenopus oocytes, we demonstrated previously that at least some of these modified nucleotides are essential for biogenesis of a functional snRNP. Here we address the subcellular site of U2 internal modification. Upon injection into the cytoplasm of oocytes, G-capped U2 that is transported to the nucleus becomes modified, whereas A-capped U2 that remains in the cytoplasm is not modified. Furthermore, by injecting U2 RNA into isolated nuclei or enucleated oocytes, we observe that U2 internal modifications occur exclusively in the nucleus. Analysis of the intranuclear localization of fluorescently labeled RNAs shows that injected wild-type U2 becomes localized to nucleoli and Cajal bodies. Both internal modification and nucleolar localization of U2 are dependent on the Sm binding site. An Sm-mutant U2 is targeted only to Cajal bodies. The Sm binding site can be replaced by a nucleolar localization signal derived from small nucleolar RNAs (the box C/D motif), resulting in rescue of internal modification as well as nucleolar localization. Analysis of additional chimeric U2 RNAs reveals a correlation between internal modification and nucleolar localization. Together, our results suggest that U2 internal modification occurs within the nucleolus.

scholarly journals The Nucleolar Localization Signal of Porcine Circovirus Type 4 Capsid Protein Is Essential for Interaction With Serine-48 Residue of Nucleolar Phosphoprotein Nucleophosmin-1

2021 ◽  
Vol 12 ◽  
Author(s):  
Jianwei Zhou ◽  
Yonghui Qiu ◽  
Ning Zhu ◽  
Linyi Zhou ◽  
Beining Dai ◽  
...  
Keyword(s):  
Porcine Circovirus Type ◽  
Cellular Proteins ◽  
Porcine Circovirus ◽  
Nucleolar Localization ◽  
Serine Residue ◽  
Nucleolar Localization Signal ◽  
Localization Signal ◽  
Charge Property ◽  
First Time ◽  
Oligomerization Domain

Porcine circovirus type 4 (PCV4) is an emerging etiological agent which was first detected in 2019. The nucleolar localization signal (NoLS) of PCV4 Cap protein and its binding host cellular proteins are still not elucidated. In the present study, we discovered a distinct novel NoLS of PCV4 Cap, which bound to the nucleolar phosphoprotein nucleophosmin-1 (NPM1). The NoLS of PCV4 Cap and serine-48 residue at the N-terminal oligomerization domain of NPM1 were necessary for PCV4 Cap/NPM1 interaction. Furthermore, the charge property of serine residue at position 48 of the NPM1 was crucial for its oligomerization and interaction with PCV4 Cap. In summary, our findings show for the first time that the PCV4 Cap NoLS and the NPM1 oligomerization determine the interaction of Cap/NPM1.

scholarly journals Nuclear Trafficking of La Protein Depends on a Newly Identified Nucleolar Localization Signal and the Ability to Bind RNA

2004 ◽  
Vol 279 (25) ◽  
pp. 26563-26570 ◽  
Author(s):  
Sven Horke ◽  
Kerstin Reumann ◽  
Michaela Schweizer ◽  
Hans Will ◽  
Tilman Heise
Keyword(s):  
Nucleolar Localization ◽  
Nuclear Trafficking ◽  
La Protein ◽  
Nucleolar Localization Signal ◽  
Localization Signal

scholarly journals Identification and Characterization of the Nucleolar Localization Signal of Autographa californica Multiple Nucleopolyhedrovirus LEF5

2019 ◽  
Vol 94 (4) ◽  
Author(s):  
Guoqing Chen ◽  
Qing Yan ◽  
Haoran Wang ◽  
Shufen Chao ◽  
Lijuan Wu ◽  
...  
Keyword(s):  
Autographa Californica ◽  
Nucleolar Localization ◽  
Sf9 Cells ◽  
Multiple Nucleopolyhedrovirus ◽  
Nucleolar Localization Signal ◽  
Viral Progeny ◽  
Localization Signal ◽  
Infected Cells ◽  
Autographa Californica Multiple Nucleopolyhedrovirus ◽  
Late Expression

ABSTRACT Autographa californica multiple nucleopolyhedrovirus (AcMNPV) late expression factor 5 (LEF5) is highly conserved in all sequenced baculovirus genomes and plays an important role in production of infectious viral progeny. In this study, nucleolar localization of AcMNPV LEF5 was characterized. Through transcriptome analysis, we identified two putative nucleolar proteins, Spodoptera frugiperda nucleostemin (SfNS) and fibrillarin (SfFBL), from Sf9 cells. Immunofluorescence analysis demonstrated that SfNS and SfFBL were localized to the nucleolus. AcMNPV infection resulted in reorganization of the nucleoli of infected cells. Colocalization of LEF5 and SfNS showed that AcMNPV LEF5 was localized to the nucleolus in Sf9 cells. Bioinformatic analysis revealed that basic amino acids of LEF5 are enriched at residues 184 to 213 and may contain a nucleolar localization signal (NoLS). Green fluorescent protein (GFP) fused to NoLS of AcMNPV LEF5 localized to the nucleoli of transfected cells. Multiple-point mutation analysis demonstrated that amino acid residues 197 to 204 are important for nucleolar localization of LEF5. To identify whether the NoLS in AcMNPV LEF5 is important for production of viral progeny, a lef5-null AcMNPV bacmid was constructed; several NoLS-mutated LEF5 proteins were reinserted into the lef5-null AcMNPV bacmid with a GFP reporter. The constructs containing point mutations at residues 185 to 189 or 197 to 204 in AcMNPV LEF5 resulted in reduction in production of infectious viral progeny and occlusion body yield in bacmid-transfected cells. Together, these data suggested that AcMNPV LEF5 contains an NoLS, which is important for nucleolar localization of LEF5, progeny production, and occlusion body production. IMPORTANCE Many viruses, including human and plant viruses, target nucleolar functions as part of their infection strategy. However, nucleolar localization for baculovirus proteins has not yet been characterized. In this study, two nucleolar proteins, SfNS and SfFBL, were identified in Sf9 cells. Our results showed that Autographa californica multiple nucleopolyhedrovirus (AcMNPV) infection resulted in redistribution of the nucleoli of infected cells. We demonstrated that AcMNPV late expression factor 5 (LEF5) could localize to the nucleolus and contains a nucleolar localization signal (NoLS), which is important for nucleolar localization of AcMNPV LEF5 and for production of viral progeny and yield of occlusion bodies.

scholarly journals NVL2 Is a Nucleolar AAA-ATPase that Interacts with Ribosomal Protein L5 through Its Nucleolar Localization Sequence

2004 ◽  
Vol 15 (12) ◽  
pp. 5712-5723 ◽  
Author(s):  
Masami Nagahama ◽  
Yoshimitsu Hara ◽  
Akihiro Seki ◽  
Takeshi Yamazoe ◽  
Yumiko Kawate ◽  
...  
Keyword(s):  
Ribosomal Protein ◽  
Mammalian Cells ◽  
Specific Interaction ◽  
Dominant Negative ◽  
Nucleolar Localization ◽  
Nuclear Localization Signals ◽  
Aaa Atpase ◽  
Nucleolar Localization Signal ◽  
Localization Signal ◽  
Ribosomal Protein L5

NVL (nuclear VCP-like protein), a member of the AAA-ATPase family, is known to exist in two forms with N-terminal extensions of different lengths in mammalian cells. Here, we show that they are localized differently in the nucleus; NVL2, the major species, is mainly present in the nucleolus, whereas NVL1 is nucleoplasmic. Mutational analysis demonstrated the presence of two nuclear localization signals in NVL2, one of which is shared with NVL1. In addition, a nucleolar localization signal was found to exist in the N-terminal extra region of NVL2. The nucleolar localization signal is critical for interaction with ribosomal protein L5, which was identified as a specific interaction partner of NVL2 on yeast two-hybrid screening. The interaction of NVL2 with L5 is ATP-dependent and likely contributes to the nucleolar translocation of NVL2. The physiological implication of this interaction was suggested by the finding that a dominant negative NVL2 mutant inhibits ribosome biosynthesis, which is known to take place in the nucleolus.

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