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Novel ZIP kinase isoform lacks leucine zipper.

ABSTRACT: Zipper-interacting protein kinase (ZIP kinase) has been thought to be involved in apoptosis and the C-terminal leucine zipper motif is important for its function. Recent studies have revealed that ZIP kinase also plays a role in regulating myosin phosphorylation. Here, we found novel ZIP kinase isoform in which the C-terminal non-kinase domain containing a leucine zipper is eliminated (hZIPK-S). hZIPK-S binds to myosin phosphatase targeting subunit 1(MYPT1) similar to the long isoform (hZIPK-L). In addition, we found that hZIPK-S as well as hZIPK-L bind to myosin. These results indicate that a leucine zipper is not critical for the binding of ZIP kinase to MYPT1 and myosin. Consistently, hZIPK-S localized with stress-fibers where they co-localized with myosin. The residues 278-311, the C-terminal side of the kinase domain common to the both isoforms, is involved in the binding to MYPT1, while the myosin binding domain is within the kinase domain. These results suggest that the newly found hZIPK-S as well as the long isoform play an important role in the regulation of myosin phosphorylation.

SUBMITTER: Takamoto N

PROVIDER: S-EPMC2758612 | biostudies-literature | 2006 Dec

REPOSITORIES: biostudies-literature

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Novel ZIP kinase isoform lacks leucine zipper.

Takamoto Norio N Komatsu Satoshi S Komaba Shigeru S Niiro Naohisa N Ikebe Mitsuo M

Archives of biochemistry and biophysics 20061016 2

Zipper-interacting protein kinase (ZIP kinase) has been thought to be involved in apoptosis and the C-terminal leucine zipper motif is important for its function. Recent studies have revealed that ZIP kinase also plays a role in regulating myosin phosphorylation. Here, we found novel ZIP kinase isoform in which the C-terminal non-kinase domain containing a leucine zipper is eliminated (hZIPK-S). hZIPK-S binds to myosin phosphatase targeting subunit 1(MYPT1) similar to the long isoform (hZIPK-L). ...[more]

PMID: 17126281

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Project description:BackgroundWild soybean (Glycine soja) is a highly adaptive plant species which can grow well in saline-alkaline soils. In soybean genome, there exist about 140 HD-Zip (Homeodomain-leucine Zipper) genes. HD-Zip transcription factor family is one of the largest plant specific superfamilies and plays important roles in response to abiotic stresses. Although HD-Zip transcription factors have been broadly reported to be involved in plant resistance to abiotic stresses like salt and drought, their roles in response to bicarbonate stress is largely unknown.ResultsFrom our previous transcriptome profile analysis of wild soybean treated by 50 mM NaHCO3, we identified an HD-Zip gene (Gshdz4) which showed high response to the alkaline stress. Our result of qRT-PCR showed that the expression of Gshdz4 was induced by alkaline stress (NaHCO3) in both leaves and roots of wild soybean. Overexpression of Gshdz4 in Arabidopsis resulted in enhanced tolerance to NaHCO3 and KHCO3 during the process of plant growth and development. However, the growths of transgenic and WT plants were not significantly different on the medium with high pH adjusted by KOH, implicating Gshdz4 is only responsible for resisting HCO3 (-) but not high pH. The transgenic plants had less MDA contents but higher POD activities and chlorophyll contents than the WT plants. Moreover, the transcript levels of stress-related genes, such as NADP-ME, H (+) -Ppase, RD29B and KIN1 were increased with greater extent in the transgenic plants than the wild plants. On the contrary, Gshdz4 overexpression lines were much sensitive to osmotic stress at seed germination and stocking stages compared to the wild plants.ConclusionsWe revealed that the important and special roles of Gshdz4 in enhancing bicarbonate tolerance and responding to osmotic stress. It is the first time to elucidate these novel functions of HD-ZIP transcription factors. All the evidences broaden our understanding of functions of HD-Zip family and provide clues for uncovering the mechanisms of high tolerance of wild soybean to saline-alkaline stresses.

Project description:Maternal embryo leucine zipper kinase (MELK) is highly expressed in a variety of malignant tumors and involved in cell cycle regulation, cell proliferation, apoptosis, tumor formation etc However, the biological effects of MELK in cervical cancer are still uninvestigated. This study aimed to explore the expression of MELK in cervical cancer, as well as its effects on the proliferation, apoptosis, DNA damage repair on cervical cancer cell line in vitro and to provide novel ideas for further improving the clinical efficacy of cervical cancer. Immunohistochemistry, Western blot, RT-qPCR, CCK8, and immunofluorescence techniques were used to detect the expression of MELK in cervical cancer tissues, paracancerous tissues, and cervical cancer cell lines. Several cervical cancer cell lines were treated with MELK knockdown by siRNA and MELK selective inhibitor OTSSP167. The effects on proliferation, apoptosis, and colony formation capacity, and tumor cell DNA damage repair-related factor were detected in cell lines. Our data showed that the high expression rate of MELK in cervical cancer patients was 56.92%. MELK expression in cervical cancer samples was significantly higher than that in paraneoplastic tissues. Highly expressed MELK correlated with the cervical histopathological grading and greatly increased with the cervical histopathological grading, from normal cervix and cervical intraepithelial neoplasia to cervical cancer. Moreover, the abnormal expression of MELK was related to cervical cancer metastasis at early stage. The knockdown of MELK with siRNA and OTSSP167 had strong inhibition effects on the proliferation, apoptosis, and colony formation of cervical cancer cells. MELK knockdown could also aggravate the DNA damage of cervical cancer cells possibly by homologous recombination repair pathway. Therefore, MELK may be a predicting marker of poor prognosis of cervical cancer and may also be a new therapeutic target for cervical cancer, providing ideas for improving the therapeutic effect of cervical cancer.

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Novel ZIP kinase isoform lacks leucine zipper.

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Novel ZIP kinase isoform lacks leucine zipper.

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