Overexpression of DEK oncogene is associated with increased proliferation of carcinoma cells and it is observed in several solid tumors due to the amplification of the 6p22.3 chromosomal region where DEK locates. Although the same chromosomal amplification occurs in multiple myeloma (MM), a plasma cell neoplasm, whether the expression and the copy number of the DEK gene are affected in MM remains elusive. We show that despite the increased copy number in CD138positive MM cells (4 out of 41 MM samples), DEK mRNA expression was down-regulated compared with that in CD138negative bone marrow (BM) cells of the same patients (P<0.0001). DEK protein was not detectable by immunohistochemistry (IHC) in CD138positive normal plasma cells or in malignant plasma cells of MM patients (n = 56) whereas it was widely expressed in normal and neoplastic B-cells. Stable knockdown or overexpression of DEK in CD138positive MM cell lines did not affect the proliferation and viability of the cells profoundly in the presence or absence of chemotherapeutic agent melphalan whereas knockdown of DEK moderately but significantly increased the expression level of CD138 (p<0.01). Decreased DEK expression in plasma cells suggests a potential role of this gene in plasma cell development and lack of detectable DEK protein by IHC could be used as a biomarker for normal and malignant plasma cells.
DEK has a short isoform (DEK isoform-2; DEK2) that lacks amino acid residues between 49–82. The full-length DEK (DEK isoform-1; DEK1) is ubiquitously expressed and plays a role in different cellular processes but whether DEK2 is involved in these processes remains elusive. We stably overexpressed DEK2 in human bone marrow stromal cell line HS-27A, in which endogenous DEKs were intact or suppressed via short hairpin RNA (sh-RNA). We have found that contrary to ectopic DEK1, DEK2 locates in the nucleus and nucleolus, causes persistent γH2AX signal upon doxorubicin treatment, and couldn’t functionally compensate for the loss of DEK1. In addition, DEK2 overexpressing cells were more sensitive to doxorubicin than DEK1-cells. Expressions of DEK1 and DEK2 in cell lines and primary tumors exhibit tissue specificity. DEK1 is upregulated in cancers of the colon, liver, and lung compared to normal tissues while both DEK1 and DEK2 are downregulated in subsets of kidney, prostate, and thyroid carcinomas. Interestingly, only DEK2 was downregulated in a subset of breast tumors suggesting that DEK2 can be modulated differently than DEK1 in specific cancers. In summary, our findings show distinct expression patterns and subcellular location and suggest non-overlapping functions between the two DEK isoforms.
IntroductionCold stresses including chilling (<20 °C) and freezing (<0 °C) temperatures negatively affect plant growth and development and seed production. Plants struggle with cold stress by improving stress tolerance (Bray et al., 2000;Chinnusamy et al., 2007). Chilling decreases the membrane fluidity by causing the impairment of unsaturated membrane lipids and freezing temperatures lead to membrane damage by severe cellular dehydration, associated with ice formation (Wang et al., 2006;Solanke and Sharma, 2008). In the cold stress pathway, cytosolic Ca 2+ is considered as an important second messenger in low-temperature signal transduction (Figure 1). Calmodulin (CaM), CaM domain-containing protein kinases (CDPKs), calcineurin B-like proteins (CBLs), and CBL-interacting protein kinases (CIPKs) are among the major Ca 2+ sensors in plants (Solanke and Sharma, 2008). Thanks to microarray technologies, a large number of cold stress-responsive genes have been identified in various plant species. These genes include three main groups: 1) signaling components (protein kinases and transcription factors), 2) functional components (enzymes in metabolic pathways, aquaporins, etc.), and 3) small noncoding RNAs, namely micro-RNAs (miRNAs) (Shen et al., 2014;Koc et al., 2015a). Moreover, many transcription factor genes, including the WRKY family, DRE-binding protein (DREB) family, zinc-finger family, ethylene-responsive element binding factor (ERF) family, MYB family, basic helix-loop-helix (bHLH) family, basic-domain leucine zipper (bZIP) family, NAC family, and homeodomain transcription factor families and retrotransposons are also activated with harsh stress conditions (Shinozaki et al., 2003;Koc et al. 2015b). A class of DREB/CBF transcription factors, which bind to DRE/CRT cis-elements in the promoter regions of target genes, is commonly known for pathways in cold-inducible genes (Maruyama et al., 2009). Recent studies of Arabidopsis thaliana have also demonstrated the importance of DREB/CBF transcription factors in cold stress. In addition, ICE1, MYB15, and CAMTA3 proteins have been identified as regulators of DREB1/CBF gene expression (Chinnusamy et al., 2007;Doherty et al., 2009). Thus, biotic/abiotic stress conditions in plants cause significant changes in global gene expression. In A. thaliana, it has been reported that nearly 30% of the transcriptome is regulated by abiotic stress, and 2409 genes have been determined to have considerable Abstract: Cold stress is a major environmental factor in plant life cycles. Nicotiana benthamiana, which belongs to the family Solanaceae, is one of the most commonly used model species in plant-microbe interaction studies. In total, 5205 differentially expressed genes were identified under cold stress in N. benthamiana. Of these, 5029 were upregulated and 176 were downregulated within four time periods (4 h, 12 h, 24 h, and 48 h). The common up-and downregulated genes were identified as 692 and 6, respectively. The functional annotations of these genes were studied and these comm...
Background/aim: Macrothrombocytopenia is an autosomal dominant disorder characterized by increased platelet size and decreased number of circulating platelets. Membrane skeleton and the link between actin filaments of the skeleton and microtubules, which consist of alpha and beta tubulin (including the tubulin beta-1 chain (TUBB1)) heterodimers, are important for the normal platelet morphology and the defects on these systems are also associated with macrothrombocytopenia. Materials and methods: In this study, we have sequenced the exons of the TUBB1 gene using the DNA isolated from peripheral blood samples of the healthy controls (n = 47) and the patients with macrothrombocytopenia (n = 37) from Turkey. TUBB1 expression levels in fractioned blood samples from the patient and healthy controls were analyzed by RT-qPCR and Western Blot. Microtubule organization of the platelets in the patient's peripheral blood smears and in the mutant TUBB1-transfected HeLa cells was analyzed by using immunofluorescence staining. Results: A new TUBB1 c.803G>T (p.T178T) variant was detected in all of the controls and patient samples. Importantly, we found 3 new heterozygous TUBB1 variants predicting amino acid substitutions, G146R (in 1 patient), E123Q (in 1 patient) and T274M (in 4 patients), the latter variant being associated with milder thrombocytopenia in cancer patients treated with paclitaxel. Ectopic expression of TUBB1 T274M/R307H variant in HeLa cells resulted in irregular microtubule organization. Conclusion: Further clinical and functional studies of the newly identified TUBB1 variants might give important insights about their pathogenicity in macrothrombocytopenia.
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