IndraLab
Statements
sparser
"To investigate the cell’s presumed requirement for NPM-Thr 198 phosphorylation in promoting the processes of growth and proliferation, we examined the effects of a non-phosphorylatable NPM mutant, T198A, in a clean cell system in which endogenous NPM had been removed by RNA interference."
sparser
"Furthermore, hyperactive Cdk2 and Cdk4 deregulate the licensing of the centrosome duplication cycle in p53-null cells by hyperphosphorylating nucleophosmin (NPM) at Thr199, as evidenced by observations that ablation of Cdk2, Cdk4, or both Cdk2 and Cdk4 abrogates that excessive phosphorylation."
sparser
"Considering the essential role of LANA in KSHV latency and suppression of lytic viral transcription, as well as the observation that v-cyclin promotes LANA-NPM interaction, we sought to address whether there is a correlation between NPM Thr199 phosphorylation, v-cyclin expression, and the extent of spontaneous lytic replication in four different patient-derived KSHV-infected PEL lines (BC-3, BCBL-1, BC-1, JSC-1), IHH (a KSHV-positive lymphoblastoid cell line), and IHE (a KSHV-negative cell line)."
sparser
"To obtain further evidence about the correlation between, v-cyclin expression levels, extent of NPM phosphorylation on Thr199, and spontaneous viral reactivation we over-expressed v-cyclin in BCBL-1 and JSC-1 cells using retroviruses expressing v-cyclin and GFP (KpBMN) or GFP (pBMN) as a control."
sparser
"To determine whether or not phosphorylation of murine NPM-Thr 198 is a cyclin E–cdk2-specific event within the context of cell cycle progression, TKO MEFs were serum-starved and synchronized in G 0 , evidenced by the cells’ low expression levels of cyclin D1 protein ( xref , lane 2)."
sparser
"Given that cyclin D1 protein expression levels were maximal at approximately 8 h after the cells’ release into serum, yet abundant levels of phospho-T198 NPM were already evident by 4-h post-stimulation, this result suggests that cyclin E–cdk2 is not the sole kinase which phosphorylates NPM-Thr 198 within the cell ( xref )."
sparser
"Interactions between RanGTP and Crm1 recruit a fraction of Crm1 to the centrosomes; xref Crm1 in turn interacts with the two NESs of NPM1, thereby recruiting NPM1 to centrosomes of nonmitotic cells. xref NPM1 is phosphorylated on Thr199 by Cdk2/cyclin E late in G 1 phase, xref which causes dissociation of the majority of NPM1 from the centrosomes, a step required for centrosome duplication to occur. xref , xref Following centrosome duplication, Thr199-phosphorylated NPM1 reassociates with the duplicated centrosomes, ensuring that reduplication does not occur."
sparser
"We also show that avrainvillamide treatment influences the localization of Thr199-phosphorylated NPM1 during mitosis, causes deregulation of centrosome duplication, and leads to an accumulation of Thr199-phosphorylated NPM1 by inhibiting its dephosphorylation by the beta isoform of protein phosphatase 1 (PP1 β )."
sparser
"These observations are consistent with the hypothesis that displacement of Thr199-phosphorylated NPM1 from duplicated centrosomes enables centrosome reduplication, and suggest that avrainvillamide alters essential cellular processes by preventing NPM1 and Crm1 from interacting with their native binding partners."
sparser
"NPM1 is phosphorylated on Thr199 by several kinases, including Cdk1, xref Cdk2, xref Cdk4, xref and Cdk6, xref and is dephosphorylated by PP1 β . xref Increases in NPM1 thr 199 phosphorylation are known to repress pre-mRNA splicing, xref reduce NPM1-mediated DNA repair activity, xref and target NPM1 to nuclear speckles. xref Over the course of our studies, we observed an apparent increase in the amount of NPM1pThr199 in avrainvillamide-treated cells ( xref ); this finding was confirmed by subsequent immunoblotting experiments ( xref )."
sparser
"In combination with the earlier result showing that NPM-Thr 198 is constitutively phosphorylated, these data indicate that this particular NPM phosphorylation site is not subject to either positive (that is, cdk-mediated) or negative (that is, ARF-directed) regulation throughout the cell cycle, but is instead constantly being phosphorylated as total levels of NPM rise in the cell."
sparser
"Although this current study demonstrates that ARF induction does not influence NPM-Thr 198 phosphorylation ( xref ), our previously published findings have shown that ARF effectively blocks NPM nucleocytoplasmic shuttling, a critical function of NPM that is essential for cellular growth and proliferation ( xref ; xref )."
sparser
"The RNA-binding activity of NPM1 is diminished after cdc2-mediated phosphorylation of Thr199 of NPM1 during mitosis, and this is suggested to link to the disassembly of nucleolus by disrupting the RNA-protein binding interaction of NPM1 (Hisaoka et al. xref ; Okuwaki et al. xref )."
| PMC
sparser
"We additionally observe that the ability of avrainvillamide to bind to Crm1 and prevent its binding to NES-containing proteins appears to disrupt the interaction between Crm1 and Thr199-phosphorylated NPM1 at key points in the cell-cycle, resulting in unregulated centrosome duplication."
sparser
"Thus, the observed effects of avrainvillamide on the subcellular localization of NPMc+ variants may represent a sublethal phenotype, while the effects of avrainvillamide on the relative levels of Thr199-phosphorylated NPM1 and on the localization of Thr199-phosphorylated NPM1 during mitosis may help explain avrainvillamide-induced antiproliferation in human cancer cells."
sparser
"Following UV-induced damage, NPM is phosphorylated at Thr199 and Thr 234/237, leading to an increase of E2F1 mRNA. xref NPM then associates with pRB and interfers with its repression of E2F1 transcription as seen by an increase of E2F1 at the promoters as well as increased expression of known E2F1 targets in DNA repair, XPC and DDB2. xref "
sparser
"In both lines, prexasertib induced a number of changes, including i) diminished CHK1 activity as manifested by reduced autophosphorylation at Ser 296 ; ii) decreased CHK1-mediated CDC25A phosphorylation, which led to increased CDC25A levels; and iii) and diminished CDK2 inhibitory phosphorylation, which resulted in increased CDK2 activity that was manifested by increased phosphorylation of the CDK2 substrate NPM1 on Thr 199 [ xref ] as shown in Fig. xref C and D ( lanes 2 and 3 vs. lane 1)."
sparser
"To investigate the role of NPM1 T199 phosphorylation in γH2AX foci formation and disassembly, we transiently transfected NPM1-null MEFs with plasmids expressing Myc-tagged wild type NPM1 or a T199 non-phosphorylatable NPM1 mutant (Myc-tagged T199A, xref ), administered 1 Gy and assayed γH2AX foci 1 hr later."
sparser
"Increased expression of NPM1 phosphorylated on Thr199 in tumor tissues from BRAF mutant colon cancer patients could be thus related to anomalies in the centrosome cycle leading to centrosome amplification, which is a common event in colon cancer linked with mutations in several cancer-associated genes including BRAF [ xref ]."
sparser
"It is well established that controlled NPM-T199 phosphorylation by Cdk2-cyclin E/A kinases normally promotes one round of centrosome duplication per cell cycle, while Cdk2 hyper-activation causes unchecked NPM-T199 phosphorylation and extra rounds of centrosome duplication xref , xref , xref ."
sparser
"We then examined the requirement of NPM phosphorylation on Thr199 for NPM-LANA interaction, by performing anti-LANA immunoprecipitation from cell extracts of U2OS cells expressing LANA and transfected with expression vectors for Myc-v-cyclin, empty vector control, and the eGFP-tagged NPM wt or its phosphosite mutant constructs used in xref ."
sparser
"Moreover, phosphorylation of NPM at T199 was lower in drug-treated resistant cells when compared to the parental, indicating that CDK2 activity may be reduced in prexasertib-resistant cells potentially accounting for the strong attenuation in markers of RS (pRPA2) and DNA damage (γH2AX) in drug-treated cultures ( xref )."