SEARCH · PubMed Health

Results for “Polo-like Kinases”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources

PubMed2025

The Role of Polo-Like Kinase 1 (PLK1) O-GlcNAcylation in Mitosis.

Polo-like kinase 1 (PLK1) is a crucial mitotic kinase that is implicated in various aspects of cell cycle. Many post-translational modifications have been identified on PLK1 to regulate its activation, stability, and localization. PLK1 has been shown previously to colocalize with the O-linked β-N-acetylglucosamine (O-GlcNAc) transferase (OGT), and OGT regulates PLK1 stability. In our recent work, we show that PLK1 is O-GlcNAcylated by click chemistry. Using stepped collisional energy/higher energy collision dissociation mass spectrometry, we mapped the PLK1 O-GlcNAc site to be T291. We further utilized fluorescent activated cell sorting and time-lapse microscopy to assess the mitotic defects of PLK1 O-GlcNAc mutants. In vivo studies in mouse xenograft demonstrated that it promoted uterine cancer tumorigenesis. In this chapter, we delineate the methodologies we used in studying PLK1 O-GlcNAcylation, including click chemistry, stepped collisional energy/higher energy collision dissociation mass spectrometry, fluorescent activated cell sorting, time-lapse microscopy, and mouse xenograft assays.

Polo-Like Kinase 1↗

PubMed1995

Polo-like kinase is a cell cycle-regulated kinase activated during mitosis.

Previously, we demonstrated that expression of polo-like kinase (PLK) is required for cellular DNA synthesis and that overexpression of PLK is sufficient to induce DNA synthesis. We now report that the endogenous levels of PLK, its phosphorylation status, and protein kinase activity are tightly regulated during cell cycle progression. PLK protein is low in G1, accumulates during S and G2M, and is rapidly reduced after mitosis. During mitosis, PLK is phosphorylated on serine, and its serine threonine kinase function is activated at a time close to that of p34cdc2. The phosphorylated form of PLK migrates with reduced mobility on SDS-polyacrylamide gel electrophoresis, and dephosphorylation by purified protein phosphatase 2A converts it to the more rapidly migrating form and reduces the total amount of PLK kinase activity. Purified p34cdc2-cyclin B complex can phosphorylate PLK protein in vitro but causes little increase in PLK kinase activity.

Amino Acid Sequence↗

PubMed1995

Identification and functional characterization of the human and murine polo-like kinase (Plk) promoter.

The Plk gene encodes a serine/theronine kinase which is located in the nucleus. Northern blot analysis linked Plk expression to the proliferative activity of cells and tissues. To analyse the transcriptional regulation of the Plk gene we have isolated several human genomic clones containing the Plk promoter. RNAse protection assays revealed three major transcription start sites within a 40 bp region centered around the 5' end of the known human cDNA and 6 minor Cap sites. A genomic fragment of 2.3 kb located 5' to the translation start sites drives the expression of the CAT-reporter in transient transfections in human (EPLC, HeLa) and mouse (NIH3T3, 32D) cell lines in an orientation dependent fashion. The 2.3 kb genomic fragment contains a CCAAT motif located 30-70 bp upstream of the Cap sites and two overlapping Sp1 sites 20 bp further upstream. Additional sequence motif homologues to binding sites of known transcription factors could be identified. In addition to the human Plk promoter, the mouse Plk promoter was isolated. The sequence alignment of the human and murine promoter revealed three regions with extensive sequence homology within a region of 300 bp immediately upstream of the Cap sites. A fourth region of homology encompassing 90 bp about 2.1 kb 5' of the Cap sites was identified as well. Deletion of various regions within the 2.3 kb promoter fragment identified several domains involved in the regulation of the human Plk promoter. The 300 bp region immediately 5' of the Cap sites which is highly conserved between mouse and man is essential for promoter activity. 3' deletions including the CCAAT site abolished promoter activity. Growing 5' deletions within the core region of the promoter reduces transcriptional activity. Furthermore, using deletion clones we identified regions 5' of the core region which enhance or silence the transcriptional activity of the core promoter.

3T3 Cells↗

PubMed2026

GSK3β and Plk1 sequentially phosphorylate ATP-citrate lyase to promote homologous recombination.

Accurate repair of DNA double-strand breaks (DSBs) by homologous recombination (HR) is essential for genome stability. Nuclear production of acetyl-coenzyme A (acetyl-CoA) by ATP-citrate lyase (ACLY) promotes HR, yet how ACLY is regulated during the DNA damage response (DDR) remains unclear. Here, we identify a phosphorylation-dependent signaling axis in which glycogen synthase kinase 3β (GSK3β) and Polo-like kinase 1 (Plk1) act sequentially on ACLY to facilitate HR-mediated repair of DSBs induced by ionizing radiation. Following AKT-dependent phosphorylation of ACLY at Ser455, GSK3β phosphorylates ACLY at Thr447, generating a docking site for Plk1, which in turn phosphorylates ACLY at Ser442. This phosphorylation cascade, enhanced by radiation, sustains histone acetylation, supports the accumulation of BRCA1 and RAD51 at DSBs, and confers cellular resistance to poly(ADP-ribose) polymerase (PARP) inhibition. Together, our findings define an AKT-GSK3β-Plk1-ACLY signaling module that links the DDR to nuclear metabolism, revealing a critical mechanism by which kinase signaling facilitates acetyl-CoA-dependent chromatin remodeling to preserve genome integrity.

Protein Serine-Threonine Kinases↗

PubMed1994

Cell cycle analysis and chromosomal localization of human Plk1, a putative homologue of the mitotic kinases Drosophila polo and Saccharomyces cerevisiae Cdc5.

polo and CDC5 are two genes required for passage through mitosis in Drosophila melanogaster and Saccharomyces cerevisiae, respectively. Both genes encode structurally related protein kinases that have been implicated in regulating the function of the mitotic spindle. Here, we report the characterization of a human protein kinase that displays extensive sequence similarity to Drosophila polo and S. cerevisiae Cdc5; we refer to this kinase as Plk1 (for polo-like kinase 1). The largest open reading frame of the Plk1 cDNA encodes a protein of 68,254 daltons, and a protein of this size is detected by immunoblotting of HeLa cell extracts with monoclonal antibodies raised against the C-terminal part of Plk1 expressed in Escherichia coli. Northern blot analysis of RNA isolated from human cells and mouse tissues shows that a single Plk1 mRNA of 2.3 kb is highly expressed in tissues with a high mitotic index, consistent with a possible function of Plk1 in cell proliferation. The Plk1 gene maps to position p12 on chromosome 16, a locus for which no associations with neoplastic malignancies are known. The Plk1 protein levels and its distribution change during the cell cycle, in a manner consistent with a role of Plk1 in mitosis. Thus, like Drosophila polo and S. cerevisiae Cdc5, human Plk1 is likely to function in cell cycle progression.

Amino Acid Sequence↗

PubMed1995

Identification by targeted differential display of an immediate early gene encoding a putative serine/threonine kinase.

Fibroblast growth factor (FGF)-1 mitogenic signal transduction is mediated in part by gene products that are specifically expressed in response to cell surface receptor binding and activation. We have used a targeted differential display method to identify FGF-1-inducible genes in murine NIH 3T3 fibroblasts. Here we report that one of these genes is predicted to encode a novel serine/threonine-specific protein kinase. This putative kinase has been named Fnk, for FGF-inducible kinase. The deduced Fnk amino acid sequence has 49, 36, 33, 32, and 22% overall identity to mouse serum-inducible kinase (Snk), mouse polo-like kinase (Plk), Drosophila polo, Saccharomyces Cdc5, and mouse Snk/Plk-akin kinase (Sak), respectively. These proteins are all members of the polo subfamily of structurally related serine/threonine kinases. The Plk, polo, Cdc5, and Sak kinases are required for cell division. FGF-1 induction of Fnk mRNA expression is first detected at 30 min after mitogen addition, reflects transcriptional activation, and does not require de novo protein synthesis. FGF-2, platelet-derived growth factor-BB, calf serum, or phorbol myristate acetate treatment of quiescent cells also induces fnk gene expression. Fnk mRNA is expressed in vivo in a tissue-specific manner, with relatively high levels detected in newborn and adult mouse skin. These results indicate that Fnk may be a transiently expressed protein kinase involved in the early signaling events required for growth factor-stimulated cell cycle progression.

3T3 Cells↗

PubMed2026

Selective Macrocyclic WEE1 Kinase Inhibitors with Strong Efficacy against Patient-Derived Colorectal Cancer Organoids.

Macrocyclization can enhance the selectivity of acyclic compounds toward structurally similar biological targets such as kinases. WEE1 regulates cellular homeostasis and is a promising target in oncology. The clinical candidate AZD1775 (1) failed to progress past Phase II trials because of patient tolerability issues, likely due to off-target inhibition of polo-like kinase 1 (PLK1). Herein, a computer-aided drug design approach was conducted to develop a macrocycle based on the 1-WEE1 X-ray cocrystal structure. Significantly enhanced WEE1 inhibitory selectivity over PLK1 was determined for leading macrocycle 2, which also demonstrated broader kinome-wide selectivity. Patient-derived organoids from colorectal cancer (CRC) peritoneal and liver metastases, treated with 2, demonstrated comparably strong or enhanced anticancer efficacy compared to that of 1. Against patient-matched normal colon vs primary CRC organoids, 2 potently and selectively treated CRC, as well as enhanced DNA damage compared to 1. Finally, the X-ray cocrystal structure of 2 bound to WEE1 validated its computationally predicted bioactive binding mode.

Humans↗

PubMed1994

Induction and down-regulation of PLK, a human serine/threonine kinase expressed in proliferating cells and tumors.

We have identified the nucleotide sequence of the cDNA encoding the human counterpart of the mouse gene Plk (polo-like kinase). The sequence of the human gene, PLK, predicts a serine/threonine kinase of 603 aa. Expression of PLK mRNA appeared to be strongly correlated with the mitotic activity of cells. Resting peripheral lymphocytes did not express the gene at all. When primary T cells were activated by phytohemagglutinin, a high level of PLK transcripts resulted within 2-3 days. In some cases, addition of interleukin 2 to these cells increased the expression of PLK mRNA further. In contrast, primary cultures of human peripheral macrophages, which were not dividing under the culture conditions applied, showed very little or no PLK mRNA. Stimulation of these cells by bacterial lipopolysaccharide, an inducer of several cytokines in macrophages, totally abrogated the expression of PLK mRNA. In line with a function of PLK mRNA expression in mitotically active cells is our finding that six immortalized cell lines examined expressed the gene. In A-431 epidermoid carcinoma cells this expression was down-regulated by serum starvation and enhanced after serum was added again. Tumors of various origin (lung, colon, stomach, smooth muscle, and esophagus as well as non-Hodgkin lymphomas) expressed high levels of PLK transcripts in about 80% of the samples studied, whereas PLK mRNA was absent in surrounding tissue, except for colon. The only normal tissues where PLK mRNA expression was observed were colon and placenta, both known to be mitotically active. No PLK transcripts were found in normal adult lung, brain, heart, liver, kidney, skeletal muscle, and pancreas. In Northern blot experiments with RNA from lymphocytes which were treated with phytohemagglutinin and cycloheximide, PLK transcripts were not detectable, suggesting that PLK is not an early growth-response gene.

Amino Acid Sequence↗

PubMed2026

Determinants of protein phosphatase 1β substrate specificity for MyPhoNE motif-containing proteins.

Phosphoprotein phosphatase 1 (PP1) forms holoenzymes composed of a catalytic subunit (PP1c) and one or two of over 200 regulatory subunits (PP1Rs). Humans express four conserved PP1c isoforms: PP1cα, PP1cβ/δ, and splice variants PP1cγ1 and PP1cγ2. To systematically characterize PP1c isoform-specific interactions, we employed mass spectrometry to identify PP1cα, PP1cβ, and PP1cγ interacting proteins, determine their isoform specificity, and assess and quantify their abundance within the PP1 holoenzyme pool. Our data show that PP1c forms hundreds of dimeric and trimeric holoenzymes, but the 10 most abundant PP1Rs make up 74% of PP1 holoenzymes, and they are highly uniform among PP1c isoforms. A key exception is myosin phosphatase N-terminal element (MyPhoNE)-containing PP1Rs, which form abundant holoenzyme complexes exclusively with PP1cβ. To define the determinants of MYPT1-PP1cβ specificity, we systematically assessed the contributions of MYPT1-PP1cβ interactions. First, we generated PP1cβ-PP1cγ chimeras and PP1cβ Tyr 305/Tyr307 point mutations to test the contribution of the PP1 C-terminal residues, and secondly, we used PP1cβ Thr197Gln (T197Q) mutation to test the effect of the MYPT1:MyPhoNE-specific interaction. Using genome editing, we demonstrate that PP1cβ T197Q-expressing cells exhibit altered PP1 holoenzyme composition and phosphorylation signaling, including increased phosphorylation of the Polo-like kinase 1 (Plk1) activation loop. Our studies further the understanding of the PP1c isoform-specific preference and demonstrate how a single amino acid change can alter PP1 holoenzyme composition and phosphorylation signaling, potentially explaining how recently discovered PP1cβ clinical variants impact PP1 biology.

MyPhoNE motif↗

PubMed2026

Targeting SUV4-20H2-mediated H4K20 methylation restrains growth and migration in pediatric high-grade astrocytomas.

Pediatric astrocytomas are characterized by increased molecular and clinical heterogeneity with epigenetic alterations contributing to aggressiveness and therapy resistance. The repressive histone mark H4K20 trimethylation (H4K20me3) and the methyltransferase SUV4-20H2 (KMT5C) are critical regulators of chromatin integrity and genome stability, with limited investigation in pediatric astrocytomas. KMT5C mRNA levels were evaluated in a publicly available pediatric gliomas database using bioinformatic analysis. Investigation of SUV4-20H2 and H4K20me3 expression was performed in a cohort of 43 pediatric astrocytoma tissues by immunohistochemistry. Their functional role and mechanism of action was investigated in pediatric glioma cell lines by using the substrate-competitive inhibitor of SUV4-20, A-196. Cell viability, apoptosis and migration were assessed using XTT, cleaved PARP, and wound healing assays, respectively. Effects of treatment on H4K20 methylation, DNA damage, mitotic stress [Polo-like kinase (PLK1) expression], and invasion markers (N-cadherin, β-catenin expression) were examined by western immunoblotting. KMT5C mRNA was significantly enriched in pediatric high-grade astrocytomas compared to low-grade tumors. A significant elevation of SUV4-20H2 and H4K20me3 expression was detected in astrocytoma tissues indicating epigenetic dysregulation contributing to malignancy. Treatment with A-196 reduced cell proliferation of pediatric glioma cell lines and induced apoptosis in a dose-dependent manner. It further impaired cell migration, accompanied by reduced N-cadherin and β-catenin expression. Mechanistically, inhibition of SUV4-20 depleted H4K20me3, inducing chromatin destabilization, replication-associated DNA damage and was associated with increased PLK1 expression, consistent with activation of a mitotic stress response. Our findings indicate that SUV4-20H2-mediated H4K20 activity in pediatric high-grade astrocytomas maintains their growth and migratory potential by regulating chromatin integrity and may serve as potential therapeutic target.

H4K20me2/3↗

PubMed1993

Identification and cloning of a protein kinase-encoding mouse gene, Plk, related to the polo gene of Drosophila.

We have determined the nucleotide sequence of a cDNA encoding a protein kinase that is closely related to the enzyme encoded by the Drosophila melanogaster mutant polo and that we have designated Plk (polo-like kinase). Plk is also related to the products of the Saccharomyces cerevisiae cell cycle gene MSD2 (CDC5) and the recently described early growth response gene Snk. Together, Plk, polo, Snk, and MSD2 define a subfamily of serine/threonine protein kinases. Plk is expressed at high levels in a number of fetal and newborn mouse tissues but is not expressed in the corresponding adult organs. With the exception of adult hemopoietic tissues, the only adult tissues in which we could detect Plk expression were ovaries and testes. Taken together, the patterns of Plk expression suggest an association with proliferating cells. Since polo is required for mitosis in Drosophila it is possible that Plk is involved in some aspect of cell cycle regulation in mammalian cells.

Amino Acid Sequence↗

PubMed1995

The conserved Schizosaccharomyces pombe kinase plo1, required to form a bipolar spindle, the actin ring, and septum, can drive septum formation in G1 and G2 cells.

We have identified a Schizosaccharomyces pombe gene with homology to the budding yeast gene CDC5, the Drosophila gene polo, and the mammalian family of genes encoding polo-like kinases. Disruption of this gene, plo1+, indicates that it is essential. Loss of plo1+ function leads to a mitotic arrest in which condensed chromosomes are associated with a monopolar spindle or to the failure of septation following the completion of nuclear division. In the latter case, cells show a failure both in the formation of an F-actin ring and in the deposition of septal material, suggesting that plo1+ function is required high in the regulatory cascade that controls septation. The overexpression of plo1+ in wild-type cells also results in the formation of monopolar spindles but also induces the formation of multiple septa without nuclear division. Septation can also be induced in the absence of mitotic commitment and concomitant spindle formation by the overexpression of plo1+ in cdc25-22 or cdc2-33 cells arrested in G2; in G1 cells arrested at Start by the cdc10-V50 mutation, or in cells lacking the cyclin B homolog cdc13 that undergo repeated S phases in the absence of mitosis.

Actins↗

PubMed2026

PLK1/FOXM1-associated tumor-cell state and macrophage-related immune features in endometrial cancer.

BACKGROUND: Polo-like kinase 1 (PLK1) and forkhead box M1 (FOXM1) have been widely studied in various cancers; however, their expression characteristics in endometrial cancer (EC) and their potential association with tumor microenvironment remodeling remain insufficiently characterized. METHODS: This study integrated The Cancer Genome Atlas uterine corpus endometrial carcinoma cohort, Gene Expression Omnibus, pan-cancer transcriptomic data, Human Protein Atlas/Clinical Proteomic Tumor Analysis Consortium, and local immunohistochemistry data to evaluate PLK1 expression and clinicopathological relevance across transcriptomic, proteomic, and histopathological data. Differential expression, survival, gene-set enrichment, transcription-factor enrichment, and immune-infiltration analyses characterized PLK1-associated features. In vitro experiments combined EC cell lines AN3CA and HEC-1A with co-immunoprecipitation, Western blotting, Transwell assays, and a THP-1 conditioned-medium model. Drug-response prediction and structure-based analysis prioritized candidate therapeutic hypotheses. RESULTS: PLK1 was consistently upregulated at both mRNA and protein levels in EC and was associated with higher tumor grade and International Federation of Gynecology and Obstetrics (FIGO) stage. In survival analysis, higher PLK1 expression was associated with poorer overall survival in univariable models but not after adjustment for age, tumor grade, and FIGO stage. Functional enrichment analysis showed that PLK1-associated genes were mainly involved in cell-cycle and mitotic processes. FOXM1 was identified as a potential candidate component of the PLK1-associated transcriptional program and was positively correlated with PLK1 expression and cell-cycle-related features. In vitro experiments supported an interaction between PLK1 and FOXM1 and suggested that FOXM1 Thr600 phosphorylation-related alterations were associated with migration and invasion phenotypes. Furthermore, the PLK1/FOXM1-associated tumor-cell state was linked to macrophage-related immune features and changes in the M2-like marker profile of THP-1-derived macrophage-like cells. Drug response analyses suggested differential predicted sensitivity patterns in PLK1-high tumors, providing candidate therapeutic hypotheses for further validation. CONCLUSION: The PLK1/FOXM1-associated tumor-cell state may represent a distinct molecular feature associated with proliferative activity, invasive phenotypes, and macrophage-related immune features in EC. This study provides preliminary evidence supporting the biological relevance of this molecular feature and highlights potential therapeutic directions for future investigation.

FoxM1↗

PubMed2025

Identification of radiation-sensitive genes as biomarkers for biodosimetry: an ex vivo analysis of TNFRSF10B, ZMAT3, POLH, and PLK2 in human blood samples.

BACKGROUND: Humans are exposed to ionizing radiation (IR), which causes direct and indirect DNA damage. Biodosimetry is a critical component of clinical care following radiation exposure, enabling accurate assessment and mitigation of health effects. The present study was conducted to investigate the ex vivo expression of the genes TNFRSF10B, ZMAT3, PLK2, and POLH in human peripheral blood samples exposed to X-radiation at doses of 0, 0.5, 2, and 4 Gy at 0, 4, 24, and 48 hours post-exposure. Investigating gene expression dynamics through biodosimetry is a novel approach that may provide insights into gene-specific responses, potentially enhancing the accuracy and sensitivity of radiation dose assessment. MATERIALS AND METHODS: Peripheral blood samples were collected from five healthy volunteers and exposed to 0, 0.5, 2, or 4 Gy radiation with a 6 MV linear accelerator. Following the extraction of RNA and cDNA synthesis, gene expression analysis via qRT‒PCR was performed. These genes were normalized against the housekeeping gene β-actin, and the ΔΔCt method was used for statistical analysis of gene expression. The data were subjected to statistical analysis, and the level of significance (p < 0.05) was determined to test the effects of dose and time on gene expression. RESULTS: The expression of the TNFRSF10B, ZMAT3, POLH, and PLK2 genes was markedly dose- and time-dependent in response to X-ray radiation in vitro. Whole-blood samples irradiated at doses of 0, 0.5, 2, and 4 Gy and analyzed at four time points, 0, 4, 24, and 48 hours, respectively, revealed marked changes in the expression levels of the genes studied, revealing the mechanisms of the response at the cellular level to ionizing radiation. Although minor inter-individual variation in gene expression was observed, it did not significantly affect the overall trends, and the results remained statistically robust. CONCLUSION: These findings highlight a robust biodosimetry framework: TNFRSF10B demonstrated the highest diagnostic performance (AUC = 0.94; sensitivity = 98%; specificity = 75%; cut-off = 1.11), making it a highly reliable biomarker for radiation exposure. PLK2 also exhibited strong discriminative capacity (AUC = 0.84; sensitivity = 90%; specificity = 80%; cut-off =2.5), particularly for minimizing false positives. ZMAT3 (AUC = 0.78; sensitivity/specificity = 75%; cut-off = 3.21) showed balanced early-phase performance, whilePOLH (AUC = 0.73; sensitivity = 80%; specificity = 60%; cut-off = 1.10) may serve as a complementary marker. Collectively, these findings support a multi-gene expression approach for accurate biodosimetric assessment and improved triage following radiation exposure.

Humans↗

PubMed2025

An anti-androgen resistance-related gene signature acts as a prognostic marker and increases enzalutamide efficacy via PLK1 inhibition in prostate cancer.

BACKGROUND: Anti-androgen resistance remains a major clinical challenge in the treatment of prostate cancer (PCa), leading to disease progression and treatment failure. Despite extensive research on resistance mechanisms, a reliable prognostic model for predicting patient outcomes and guiding therapeutic strategies is still lacking. This study aimed to develop a novel gene signature related to anti-androgen resistance and evaluate its prognostic and therapeutic implications. METHODS: Anti-androgen resistance-related differentially expressed genes (ARRDEGs) were identified through transcriptomic analysis of enzalutamide- and dual enzalutamide abiraterone-resistant PCa cell lines from the GEO database. Functional enrichment analysis was performed to determine the biological roles of these genes. A prognostic gene signature was developed using univariate Cox regression, LASSO, and multivariate Cox regression models. The model was validated in independent PCa cohorts from The Cancer Genome Atlas (TCGA). Additionally, we assessed the correlation between the signature, immune infiltration, immune checkpoint expression, and drug sensitivity. The efficacy of PLK1 inhibition combined with enzalutamide was further explored using in vitro and in vivo experiments. RESULTS: We identified 304 ARRDEGs, from which three key genes (LMNB1, SSPO, and PLK1) were selected to construct a prognostic signature. This gene signature effectively stratified PCa patients into high- and low-risk groups, with the high-risk group exhibiting shorter recurrence-free survival and distinct immune characteristics. High-risk patients demonstrated elevated immune checkpoint expression (B7H3, CTLA-4, B7-1, and TIGIT), increased M2 macrophage infiltration, and enhanced sensitivity to chemotherapy and targeted therapy. Mechanistically, PLK1 inhibition potentiated the antitumor effect of enzalutamide by downregulating SLC7A11 and inducing ferroptosis, providing a potential therapeutic strategy to overcome anti-androgen resistance. CONCLUSION: We established a novel ARRDEGs-based prognostic signature that predicts PCa progression and response to chemotherapy and targeted therapy. The integration of this signature with immune profiling and drug sensitivity analysis provides a valuable tool for precision oncology in PCa. Our findings highlight the potential of PLK1 inhibition as a therapeutic strategy to enhance enzalutamide efficacy and overcome resistance.

Humans↗

PubMed1995

Protein kinases in the control of mitosis: focus on nucleocytoplasmic trafficking.

The eukaryotic cell nucleus is a highly dynamic organelle. This is illustrated most dramatically during mitosis, when the nuclear envelope breaks down, the nuclear lamina disassembles, chromosomes condense, and a microtubule-based spindle apparatus distributes sister chromatids to the dividing daughter cells. Many of these dramatic changes in nuclear architecture and microtubule organization are controlled by phosphorylation and dephosphorylation events. Whereas the cardinal role of cyclin-dependent kinases (CDKs) in the regulation of mitosis is well established, there is now clear evidence for the requirement of additional mitotic protein kinases. Studies into the regulation of CDKs and other mitotic kinases have revealed that these enzymes undergo cell cycle dependent changes in subcellular distribution, suggesting that localization may contribute to regulating their activities. This article describes some recent findings relating to the nucleocytoplasmic translocation of CDK/cyclin complexes at the onset of mitosis. In addition, it summarizes recent information on two novel human protein kinases which have been implicated in the control of mitotic progression.

Amino Acid Sequence↗

PubMed1995

Murine polo like kinase 1 gene is expressed in meiotic testicular germ cells and oocytes.

To identify key molecules that regulate germ cell proliferation and differentiation, we have attempted to isolate protein kinase genes preferentially expressed in germ line cells. One such cDNA cloned from murine embryonic germ(EG) cells encodes a nonreceptor type serine/threonine kinase and is predominantly expressed in the testis, ovary, and spleen of adult mouse. The nucleotide sequence of the entire coding regions shows that this clone, designated Plk1(polo like kinase 1), is identical with STPK13 previously cloned from murine erythro-leukemia cells. The protein encoded by Plk1 is closely related to the product of Drosophila polo that plays a role in mitosis and meiosis. To define the role of Plk1 in germ cell development, we have examined its expression in murine gonads by in situ hybridization. Here we show that the Plk1 gene is specifically expressed in spermatocytes of diplotene and diakinesis stage, in secondary spermatocytes, and in round spermatids in testes. It is also expressed in growing oocytes and ovulated eggs. The pattern of expression of the Plk1 gene suggests that the gene product is involved in completion of meiotic division, and like the Drosophila polo protein, is a maternal factor active in embryos at the early cleavage stage.

Animals↗

PubMed1995

Plk is an M-phase-specific protein kinase and interacts with a kinesin-like protein, CHO1/MKLP-1.

PLK (STPK13) encodes a murine protein kinase closely related to those encoded by the Drosophila melanogaster polo gene and the Saccharomyces cerevisiae CDC5 gene, which are required for normal mitotic and meiotic divisions. Affinity-purified antibody generated against the C-terminal 13 amino acids of Plk specifically recognizes a single polypeptide of 66 kDa in MELC, NIH 3T3, and HeLa cellular extracts. The expression levels of both poly(A)+ PLK mRNA and its encoded protein are most abundant about 17 h after serum stimulation of NIH 3T3 cells. Plk protein begins to accumulate at the S/G2 boundary and reaches the maximum level at the G2/M boundary in continuously cycling cells. Concurrent with cyclin B-associated cdc2 kinase activity, Plk kinase activity sharply peaks at the onset of mitosis. Plk enzymatic activity gradually decreases as M phase proceeds but persists longer than cyclin B-associated cdc2 kinase activity. Plk is localized to the area surrounding the chromosomes in prometaphase, appears condensed as several discrete bands along the spindle axis at the interzone in anaphase, and finally concentrates at the midbody during telophase and cytokinesis. Plk and CHO1/mitotic kinesin-like protein 1 (MKLP-1), which induces microtubule bundling and antiparallel movement in vitro, are colocalized during late M phase. In addition, CHO1/MKLP-1 appears to interact with Plk in vivo and to be phosphorylated by Plk-associated kinase activity in vitro.

3T3 Cells↗