The major phosphorylation site of nucleophosmin (B23) is phosphorylated by a nuclear kinase II.
Ontology highlight
ABSTRACT:
SUBMITTER: Chan PK
PROVIDER: S-EPMC1131759 | biostudies-other | 1990 Sep
REPOSITORIES: biostudies-other
Similar Datasets
Project description:CENP-W was originally identified as a putative oncogene, cancer-upregulated gene 2 (CUG2) that was commonly up-regulated in many cancer tissues. Recently, CENP-W has also been identified as a new centromeric component that interacts with CENP-T. As a complex with CENP-T, CENP-W plays crucial roles in assembly of the functional kinetochore complex. In this study, the subnuclear localization of CENP-W was extensively analyzed using various approaches. We found that ectopically expressed CENP-W primarily accumulated in the nucleolus and remained substantially associated with the nucleolus in stable cells. The following fractionation study also showed that CENP-W is associated with RNA as well as DNA. Moreover, a considerable amount of CENP-W was found in the nuclear mesh-like structure, nuclear matrix, possibly indicating that CENP-W participates in diverse subnuclear activities. Finally, biochemical affinity binding analysis revealed that CENP-W specifically interacts with the nucleolar phosphoprotein, nucleophosmin (B23). Depletion of cellular B23 by siRNA treatment induced a dramatic decrease of CENP-W stability and severe mislocalization during prophase. Our data proposed that B23 may function in the assembly of the kinetochore complex by interacting with CENP-W during interphase.
| S-EPMC3234906 | biostudies-literature
Project description:Aurora A (AurA) is a major mitotic protein kinase involved in centrosome maturation and spindle assembly. Nucleophosmin/B23 (NPM) is a pleiotropic nucleolar protein involved in a variety of cellular processes including centrosome maturation. In the present study, we report that NPM is a strong activator of AurA kinase activity. NPM and AurA coimmunoprecipitate and colocalize to centrosomes in G2 phase, where AurA becomes active. In contrast with previously characterized AurA activators, NPM does not trigger autophosphorylation of AurA on threonine 288. NPM induces phosphorylation of AurA on serine 89, and this phosphorylation is necessary for activation of AurA. These data were confirmed in vivo, as depletion of NPM by ribonucleic acid interference eliminated phosphorylation of CDC25B on S353 at the centrosome, indicating a local loss of AurA activity. Our data demonstrate that NPM is a strong activator of AurA kinase activity at the centrosome and support a novel mechanism of activation for AurA.
| S-EPMC3317798 | biostudies-other
Project description:We report that during assembly of HPV16 pseudovirus (PsV) the minor capsid protein, L2, interacts with the host nucleolar protein nucleophosmin (NPM1/B23). Exogenously-expressed L2 colocalized with NPM1, a complex containing both proteins could be immunoprecipitated, and L2 could redirect to the nucleus NPM1 that was pharmacologically or genetically restricted to the cytoplasm. Coexpression of the major capsid protein, L1, prevented both the colocalization and the biochemical association, and L1 pentamers could displace L2 from L2/NPM1 complexes attached to a nuclear matrix. HPV16 PsV that was produced in a cell line with reduced NPM1 levels had significantly lower infectivity compared to PsV produced in the parental cell line, although the PsV preparations had comparable L1 and L2 ratios and levels of encapsidated DNA. The PsV produced in NPM1-deficient cells showed increased trypsin sensitivity and exhibited decreased L2 levels during endocytosis. These results suggest a critical role for NPM1 in establishing the correct interactions between L2 and L1 during HPV capsid assembly. A decrease in cellular levels of NPM1 results in the formation of seemingly normal, but unstable, capsids that result in a premature loss of L2, thus inhibiting successful infection. No role for NPM1 in HPV infectious entry was found.
| S-EPMC4934132 | biostudies-literature
Project description:Nucleophosmin/B23, an abundant nucleolar protein, plays multiple roles in cell growth and proliferation, and yet, little has been studied about its function in regulating dynamics of microtubules. Here, we report that B23 directly interacts with Eg5, a member of the kinesin family, in the cytosol. The DNA/RNA binding domain of B23 and the motor domain of Eg5 were found to be involved in their interaction. Both in vivo and in vitro evidences showed that B23 acts as an upstream regulator of Eg5 in promoting microtubule polymerization. Moreover, we further demonstrated that B23 regulates microtubule dynamics by directly inhibiting Eg5 ATPase activity.
| S-EPMC2885184 | biostudies-literature
Project description:The nucleolus is a subnuclear compartment with multiple cellular functions, including ribosome biogenesis. USP36 is a deubiquitylating enzyme that localizes to nucleoli and plays an essential role in regulating the structure and function of the organelle. However, how the localization of USP36 is regulated remains unknown. Here, we identified a short stretch of basic amino acids (RGKEKKIKKFKREKRR) that resides in the C-terminal region of USP36 and serves as a nucleolar localization signal for the protein. We found that this motif interacts with a central acidic region of nucleophosmin/B23, a major nucleolar protein involved in various nucleolar functions. Knockdown of nucleophosmin/B23 resulted in a significant reduction in the amount of USP36 in nucleoli, without affecting the cellular USP36 level. This was associated with elevated ubiquitylation levels of fibrillarin, a USP36 substrate protein in nucleoli. We conclude that nucleophosmin/B23 recruits USP36 to nucleoli, thereby serving as a platform for the regulation of nucleolar protein functions through ubiquitylation/deubiquitylation.
| S-EPMC2788843 | biostudies-literature
Project description:The nucleophosmin (NPM)/nucleoplasmin family of nuclear chaperones has three members: NPM1, NPM2, and NPM3. Nuclear chaperones serve to ensure proper assembly of nucleosomes and proper formation of higher order structures of chromatin. In fact, this family of proteins has such diverse functions in cellular processes such as chromatin remodeling, ribosome biogenesis, genome stability, centrosome replication, cell cycle, transcriptional regulation, apoptosis, and tumor suppression. Of the members of this family, NPM1 is the most studied and is the main focus of this review. NPM2 and NPM3 are less well characterized, and are also discussed wherever appropriate. The structure–function relationship of NPM proteins has largely been worked out. Other than the many processes in which NPM1 takes part, the major interest comes from its involvement in human cancers, particularly acute myeloid leukemia (AML). Its significance stems from the fact that AML with mutated NPM1 accounts for ∼30% of all AML cases and usually has good prognosis. Its clinical importance also comes from its involvement in virus replication, particularly in the era of outbreaks of infectious diseases.
| S-EPMC7121557 | biostudies-literature
Project description:CCN2/CTGF is a multifunctional factor that plays a crucial role in the growth and differentiation of chondrocytes. The chicken ccn2 gene is regulated not only at the transcriptional level but also by the interaction between a posttranscriptional element in the 3' untranslated region (3'-UTR) and a cofactor. In the present study, we identified a nucleophosmin (NPM) (also called B23) as this cofactor. Binding of NPM to the element was confirmed, and subsequent analysis revealed a significant correlation between the decrease in cytosolic NPM and the increased stability of the ccn2 mRNA during chondrocyte differentiation in vivo. Furthermore, recombinant chicken NPM enhanced the degradation of chimeric RNAs containing the posttranscriptional cis elements in a chicken embryonic fibroblast extract in vitro. It is noteworthy that the RNA destabilization effect by NPM was far more prominent in the cytosolic extract of chondrocytes than in that of fibroblasts, representing a chondrocyte-specific action of NPM. Stimulation by growth factors to promote differentiation changed the subcellular distribution of NPM in chondrocytes, which followed the expected patterns from the resultant change in the ccn2 mRNA stability. Therefore, the present study reveals a novel aspect of NPM as a key player in the posttranscriptional regulation of ccn2 mRNA during the differentiation of chondrocytes.
| S-EPMC2547004 | biostudies-literature
Project description:By taking advantage of its ability to be retained by ATP-agarose, we have demonstrated that nucleophosmin/B23 is capable of binding ATP. The specificity of the binding was confirmed by the absence of significant binding to AMP-agarose and by its loss when nucleophosmin/B23 in nuclear extracts was preincubated with ATP. Preincubation of the nuclear extracts with other ribonucleotide triphosphates (GTP, CTP, UTP) did not compete for the binding of nucleophosmin/B23 to ATP-agarose. The purified recombinant nucleophosmin/B23 was also able to be retained by ATP-agarose. The Kd for binding of ATP to the purified recombinant nucleophosmin/B23, on the basis of retention on a nitrocellulose membrane, was 86.5+/-8.3 microM; the number of binding sites was 0.68 per nucleophosmin/B23 protein molecule. To determine the possible ATP-binding site of nucleophosmin/B23, various deletion clones including the two mutants in which the putative ATP-binding sequence had been deleted were constructed. Deletion of the portions of the molecule (residues 83-152 and 185-240) had little effect on the ATP binding. The C-terminal deleted mutant (residue 242 to the C-terminus deleted) lost most of its ability to be retained by ATP-agarose and to bind [alpha-32P]ATP on a nitrocellulose membrane. The results indicate that the C-terminal portion (residues 242-294) contains the essential ATP-binding site of nucleophosmin/B23.
| S-EPMC1219074 | biostudies-other
Project description:PNRC (proline-rich nuclear receptor coregulatory protein) was primarily identified as a coactivator of nuclear receptors (NRs) by our laboratory, which enhances NR-mediated transcription by RNA polymerase II. Recent study has shown that PNRC also stimulates RNA polymerase III-dependent transcription through interaction with the subunit RPC39 of RNA polymerase III. Here, we report that PNRC accumulates in the nucleolus and its depletion by small interfering RNA (siRNA) impairs pre-rRNA transcription by RNA polymerase I. We identified the sequence at position 94-101 ((94)PKKRRKKK(101)) of PNRC as its nucleolar localization sequence (NoLS). Fusion of this sequence to GFP directed GFP to the nucleolus. Characterization of the NoLS revealed that the stretches of six successive basic residues are sufficient to function as a NoLS. Through co-immunoprecipitation assay, we demonstrated that the NoLS is necessary and sufficient to mediate the association of PNRC with B23/nucleophosmin. Moreover, B23 depletion by siRNA disrupted the accumulation of PNRC in the nucleolus. Together, our study indicates that PNRC is a novel nucleolar protein that might be involved in regulation of pre-rRNA synthesis, and it localizes to the nucleolus by interaction with B23 via its NoLS. Our study also suggests that the stretches of six successive basic residues (lysine and/or arginine) could function as NoLS.
| S-EPMC3085350 | biostudies-literature
Project description:Human cytomegalovirus (HCMV) is a ubiquitous pathogen belongs to betaherpesvirus subfamily. RNA2.7 is a highly conserved long non-coding RNA accounting for more than 20% of total viral transcripts. In our study, functions of HCMV RNA2.7 were investigated by comparison of host cellular transcriptomes between cells infected with HCMV clinical strain and RNA2.7 deleted mutant. It was demonstrated that RNA polymerase II (Pol II)-dependent host gene transcriptions were significantly activated when RNA2.7 was removed during infection. A 145 nt-in-length motif within RNA2.7 was identified to inhibit the phosphorylation of Pol II Serine-2 (Pol II S2) by reducing the interaction between Pol II and phosphorylated cyclin-dependent kinase 9 (pCDK9). Due to the loss of Pol II S2 phosphorylation, cellular DNA pre-replication complex (pre-RC) factors, including Cdt1 and Cdc6, were significantly decreased, which prevented more cells from entering into S phase and facilitated viral DNA replication. Our results provide new insights of HCMV RNA2.7 functions in regulation of host cellular transcription.
| S-EPMC9243627 | biostudies-literature