Centrosomes organize the bipolar mitotic spindle, and centrosomal defects cause chromosome instability. Protein phosphorylation modulates centrosome function, and we provide a comprehensive map of phosphorylation on intact yeast centrosomes (18 proteins). Mass spectrometry was used to identify 297 phosphorylation sites on centrosomes from different cell cycle stages. We observed different modes of phosphoregulation via specific protein kinases, phosphorylation site clustering, and conserved phosphorylated residues. Mutating all eight cyclin-dependent kinase (Cdk)–directed sites within the core component, Spc42, resulted in lethality and reduced centrosomal assembly. Alternatively, mutation of one conserved Cdk site within γ-tubulin (Tub4-S360D) caused mitotic delay and aberrant anaphase spindle elongation. Our work establishes the extent and complexity of this prominent posttranslational modification in centrosome biology and provides specific examples of phosphorylation control in centrosome function.
Like many asymmetrically dividing cells, budding yeast segregates mitotic spindle poles nonrandomly between mother and daughter cells. During metaphase, the spindle positioning protein Kar9 accumulates asymmetrically, localizing specifically to astral microtubules emanating from the old spindle pole body (SPB) and driving its segregation to the bud. Here, we show that the SPB component Nud1/centriolin acts through the mitotic exit network (MEN) to specify asymmetric SPB inheritance. In the absence of MEN signaling, Kar9 asymmetry is unstable and its preference for the old SPB is disrupted. Consistent with this, phosphorylation of Kar9 by the MEN kinases Dbf2 and Dbf20 is not required to break Kar9 symmetry but is instead required to maintain stable association of Kar9 with the old SPB throughout metaphase. We propose that MEN signaling links Kar9 regulation to SPB identity through biasing and stabilizing the age-insensitive, cyclin-B-dependent mechanism of symmetry breaking.
Abstract. Accumulating evidence reveals that long non-coding RNA (lncRNA) is essential for tumorigenesis and progression, but little is known about its roles and mechanisms in metastatic colorectal cancer (CRC). This study aimed to detect expression level and prognostic role of lncRNA-CTD903 in CRC patients, which was selected based on one microarray data. The effects on cell invasion, migration and proliferation were investigated after silencing or overexpression of CTD903 in CRC cell lines. We also observed the EMT (epithelial-mesenchymal transition) phenomenon and effect on cell adhesion. The associations between CTD903 and EMT markers, such as E-cadherin, N-cadherin, β-catenin, ZEB1, ZO-1, Snail, and Twist, were determined by western blotting. Our results showed lncRNA-CTD903 expression was strongly upregulated in 115 CRC patients, comparing to adjacent normal tissues. CTD903 was proven to be an independent predicted factor of favorable prognosis in CRC patients by using multivariate Cox proportional hazards model. After knockdown of CTD903 in RKO and SW480, both cell invasion and migration increased, and cells exhibited EMT-like appearance, along with reduced adhering ability. Moreover, overexpression of CTD903 in DLD1 and HCT116 reversed these phenotypes. Furthermore, downregulation of CTD903 enhanced Wnt/β-catenin activation and subsequently increased transcription factors (Twist and Snail) expression, along with increased mesenchymal marker Vimentin and decreased epithelial marker ZO-1 level, while overexpressed CTD903 confirmed these associations.In conclusion, this study shows that LncRNA-CTD903 acts as a tumor suppressor in CRC and can inhibit cell invasion and migration through repressing Wnt/β-catenin signaling, which plays important roles in EMT and CRC metastasis.
Sample was prepared, and lipids were extracted according to the methyl tert-butyl ether (MTBE) method. Briefly, samples were homogenized with 200 µL water and 240 µL methanol (Thermo Fisher,
TRIM58 is a member of the tripartite motif protein (TRIM) family of E3 ubiquitin ligases. Aberrant gene methylation of TRIM58 has been reported in liver and lung cancer and indicates a poor patient prognosis. However, the expression level and functional role of TRIM58 in colorectal cancer (CRC) have yet to be elucidated. In the present study, we found that TRIM58 expression was significantly suppressed in human CRC and was inversely correlated with CRC progression. Additionally, overall survival was significantly reduced in patients with low TRIM58 expression in CRC tumors. In vitro studies demonstrated that ectopic TRIM58 overexpression strongly inhibited CRC cell invasion but had minimal effects on cell proliferation, colonization and migration. Furthermore, TRIM58 suppression enhanced the expression of epithelial-to-mesenchymal transition (EMT) and matrix metalloproteinase (MMP) genes. Thus, our findings suggest that TRIM58 is a potential prognostic marker of CRC and functions as a tumor-suppressor gene via inhibition of cancer cell invasion through EMT and MMP activation.
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