Upstream open reading frames (uORFs) are often translated ahead of the main ORF of a gene and regulate gene expression, sometimes in a condition-dependent manner, but such a role for the minimum uORF (hereafter referred to as AUG-stop) in living organisms is currently unclear. Here, we show that AUG-stop plays an important role in the boron (B)-dependent regulation of NIP5;1, encoding a boric acid channel required for normal growth under low B conditions in Arabidopsis thaliana High B enhanced ribosome stalling at AUG-stop, which was accompanied by the suppression of translation and mRNA degradation. This mRNA degradation was promoted by an upstream conserved sequence present near the 5'-edge of the stalled ribosome. Once ribosomes translate a uORF, reinitiation of translation must take place in order for the downstream ORF to be translated. Our results suggest that reinitiation of translation at the downstream NIP5;1 ORF is enhanced under low B conditions. A genome-wide analysis identified two additional B-responsive genes, SKU5 and the transcription factor gene ABS/NGAL1, which were regulated by B-dependent ribosome stalling through AUG-stop. This regulation was reproduced in both plant and animal transient expression and cell-free translation systems. These findings suggest that B-dependent AUG-stop-mediated regulation is common in eukaryotes.

Cellular homeostasis is maintained by the highly organized cooperation of intracellular trafficking systems, including COPI, COPII, and clathrin complexes. COPI is a coatomer protein complex responsible for intracellular protein transport between the endoplasmic reticulum and the Golgi apparatus. The importance of such intracellular transport mechanisms is underscored by the various disorders, including skeletal disorders such as cranio-lenticulo-sutural dysplasia and osteogenesis imperfect, caused by mutations in the COPII coatomer complex. In this article, we report a clinically recognizable craniofacial disorder characterized by facial dysmorphisms, severe micrognathia, rhizomelic shortening, microcephalic dwarfism, and mild developmental delay due to loss-of-function heterozygous mutations in ARCN1, which encodes the coatomer subunit delta of COPI. ARCN1 mutant cell lines were revealed to have endoplasmic reticulum stress, suggesting the involvement of ER stress response in the pathogenesis of this disorder. Given that ARCN1 deficiency causes defective type I collagen transport, reduction of collagen secretion represents the likely mechanism underlying the skeletal phenotype that characterizes this condition. Our findings demonstrate the importance of COPI-mediated transport in human development, including skeletogenesis and brain growth.

Abstract. ptprd is a receptor-type tyrosine-protein phosphatase. recent analyses of comprehensive mutations and copy numbers have revealed that PTPRD is frequently mutated and homozygously deleted in various types of cancer, including glioblastoma, melanoma, breast and colon cancer. however, the molecular functions of ptprd in cancer progression have yet to be elucidated. herein, ptprd suppressed colon cancer cell migration and was required for appropriate cellcell adhesion. in addition, ptprd regulated cell migration in cooperation with β-catenin/tcF signaling and its target cd44. Furthermore, expression levels of ptprd were down-regulated in highly invasive cancers and were significantly correlated with patient survival. Our findings suggest that PTPRD is required for colon cancer invasion and progression. Introductionreceptor-type tyrosine-protein phosphatase δ (ptprd) is a receptor type tyrosine-protein phosphatase (rptp) that is composed of a cell adhesion molecule-like extracellular domain and two cytoplasmic protein tyrosine phosphatase (ptp) domains (1,2). ptprd is predominantly expressed in the brain and is known to be involved in the guidance and termination of motor neurons during embryonic development (3). ptprd knockout mice exhibit impaired learning and memory, also indicating that ptprd is essential for the organization of neural circuits (4).it has been shown that PTPRD is frequently mutated in various types of cancer, including lung, colon cancer and glioblastoma (5-8). Furthermore, homozygous deletions and epigenetic silencing of PTPRD are also found in these cancers, indicating that PTPRD is a tumor-suppressor gene (9-11).however, the molecular functions of ptprd in cancer progression are not fully understood.the extracellular domain of ptprd was reported to enhance neurite outgrowth in an isoform-specific manner (12). the intracellular domain of ptprd interacts with cytoskeletal rearrangement factors, such as the liprin-α family of proteins and mim (missing in metastasis, also known as mtSS1) (13-15). these observations indicate that ptprd regulates the adhesion and migration of cancer cells and that the loss of ptprd function promotes cancer progression. in the present study, ptprd suppressed colon cancer cell migration and was found to be required for appropriate cell-cell adhesion. ptprd also regulated cell migration in cooperation with β-catenin/tcF signaling and its target cd44. cd44 is a receptor for hyaluronic acid and other extracellular matrix (Ecm) proteins, and is reported to be involved in cancer invasion and metastasis (16). Furthermore, the expression levels of ptprd were decreased in highly invasive cancers compared to less invasive cases, and were significantly correlated with patient survival. these results implicate ptprd in colon cancer cell invasion and progression. Materials and methodsCell culture and transfection. dld-1 cells were cultured in rpmi medium supplemented with 10% fetal bovine serum (FBS). HEK293T cells were cultured in Dulbecco's modified Eagle's medium (dm...

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AIM:To investigate the clinical significance of BMP and activin membrane-bound inhibitor (BAMBI) which is a pseudoreceptor of transforming growth factorbeta (TGF-β) type Ⅰ receptors and acts as a negative regulator of TGF-β signaling and expression aberrantly elevated in colorectal cancers (CRCs). We studied BAMBI expression in CRCs. METHODS:We studied BAMBI expression in 183 surgically resected CRCs by immunochemical and immunoblotting analyses using a generated monoclonal anti-BAMBI antibody. Commercially available anti-β-catenin and anti-p53 antibodies were also applied for immunochemical analyses as a comparison control. RESULTS:Immunohistochemical analysis revealed that BAMBI expression was observed in 148 (80.8%), and strong BAMBI expression was observed in 46% of the CRCs. Strong BAMBI expression was positively correlated with histological type, depth of invasion, lymph node metastases, and tumor node metastasis (TNM) stage (P < 0.05). Clear associations were found between BAMBI and β-catenin (P = 0.035) and p53 (P = 0.049) expression. In curatively resected CRC, 5-year recurrence-free survival was 51.9% (P = 0.037) for strong BAMBI expression compared to 79.8% for weak BAMBI expression. In the Cox's multivariate analysis, lymph node metastases (RR 6.685; P < 0.001) and depth of invasion (RR 14.0; P = 0.013) were significant indicators for recurrence, and strong BAMBI expression (RR 2.26; P = 0.057) tended to be significant. CONCLUSION: BAMBI was linked to a potentially aggressive tumor phenotype and predicted tumor recurrence and cancer-related death in CRC. BAMBI expression might be applicable in the routine clinical setting of CRC.