18 research outputs found

    Glucose sensor O-GlcNAcylation coordinates with phosphorylation to regulate circadian clock.

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    Posttranslational modifications play central roles in myriad biological pathways including circadian regulation. We employed a circadian proteomic approach to demonstrate that circadian timing of phosphorylation is a critical factor in regulating complex GSK3β-dependent pathways and identified O-GlcNAc transferase (OGT) as a substrate of GSK3β. Interestingly, OGT activity is regulated by GSK3β; hence, OGT and GSK3β exhibit reciprocal regulation. Modulating O-GlcNAcylation levels alter circadian period length in both mice and Drosophila; conversely, protein O-GlcNAcylation is circadianly regulated. Central clock proteins, Clock and Period, are reversibly modified by O-GlcNAcylation to regulate their transcriptional activities. In addition, O-GlcNAcylation of a region in PER2 known to regulate human sleep phase (S662-S674) competes with phosphorylation of this region, and this interplay is at least partly mediated by glucose levels. Together, these results indicate that O-GlcNAcylation serves as a metabolic sensor for clock regulation and works coordinately with phosphorylation to fine-tune circadian clock

    A PERIOD3 variant causes a circadian phenotype and is associated with a seasonal mood trait.

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    In humans, the connection between sleep and mood has long been recognized, although direct molecular evidence is lacking. We identified two rare variants in the circadian clock gene PERIOD3 (PER3-P415A/H417R) in humans with familial advanced sleep phase accompanied by higher Beck Depression Inventory and seasonality scores. hPER3-P415A/H417R transgenic mice showed an altered circadian period under constant light and exhibited phase shifts of the sleep-wake cycle in a short light period (photoperiod) paradigm. Molecular characterization revealed that the rare variants destabilized PER3 and failed to stabilize PERIOD1/2 proteins, which play critical roles in circadian timing. Although hPER3-P415A/H417R-Tg mice showed a mild depression-like phenotype, Per3 knockout mice demonstrated consistent depression-like behavior, particularly when studied under a short photoperiod, supporting a possible role for PER3 in mood regulation. These findings suggest that PER3 may be a nexus for sleep and mood regulation while fine-tuning these processes to adapt to seasonal changes

    BRCA1 mutations in women with familial or early-onset breast cancer and BRCA2 mutations in familial cancer in Estonia

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    <p>Abstract</p> <p>Background</p> <p>The aim of this study was to identify BRCA1 and BRCA2 mutations in the Estonian population. We analyzed genetic data and questionnaire from 64 early-onset (< 45 y) breast cancer patients, 47 familial cases (patients with breast or ovarian cancer and a case of these cancers in the family), and 33 predictive cases (patients without breast or ovarian cancer, with a family history of such diseases) from Estonia for mutations in the BRCA1 gene. A sub-set of familial cases and predictive cases were also analyzed for mutations in the BRCA2 gene.</p> <p>Methods</p> <p>For mutation detection, we used the Polymerase Chain Reaction-Single Stranded Conformation Polymorphism Heteroduplex Analysis (PCR-SSCP-HD), followed by direct DNA sequencing.</p> <p>Results</p> <p>We identified three clinically important mutations in the BRCA1 gene, including seven occurrences of the c.5382insC mutation, three of c.4154delA, and one instance of c.3881_3882delGA. We also detected six polymorphisms: c.2430T>C, c.3232A>G, c.4158A>G, c.4427T>C, c.4956A>G, and c.5002T>C. Four sequence alterations were detected in introns: c.560+64delT, c.560+ [36-38delCTT, 52-63del12], c.666-58delT, and c.5396+60insGTATTCCACTCC. In the BRCA2 gene, two clinically important mutations were found: c.9610C>T and c.6631delTTAAATG. Additionally, two alterations (c.7049G>T and c.7069+80delTTAG) with unknown clinical significance were detected.</p> <p>Conclusions</p> <p>In our dataset, the overall frequency of clinically important BRCA1 mutations in early-onset patients, familial cases, and predictive testing was 7.6% (144 cases, 11 mutation carriers). Pathogenic mutations were identified in 4 of the 64 early-onset breast cancer cases (6.3%). In familial cases, clinically important mutations in the BRCA1 gene were found in 6 of the 47 individuals analyzed (12.8%). In predictive cases, 1 clinically important mutation was detected in 33 individuals studied (3%). The occurrence of clinically important mutations in BRCA2 in familial cases of breast cancer was 2 of the 16 individuals analyzed (12.5%).</p

    Characterizing Sialic Acid Variants at the Glycopeptide Level

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    Beam-type collision-induced dissociation (CID) data of intact glycopeptides isolated from mouse liver tissue are presented to illustrate characteristic fragmentation of differentially sialylated glycopeptides. Eight glycoforms of an O-linked glycopeptide from Nucleobindin-1 are distinguished on the basis of the precursor masses and characteristic oxonium ions. We report that all sialic acid variants are prone to neutral loss from the charge reduced species in electron-transfer dissociation (ETD) fragmentation. We show how changes in sialic acid composition affect reverse phase chromatographic retention times: sialic acid addition increases glycopeptide retention times significantly; replacing the N-acetylneuraminic acid with the N-glycolyl variant leads to slightly reduced retention times, while O-acetylated sialic acid-containing glycoforms are retained longer. We then demonstrate how MS-Filter in Protein Prospector can use these diagnostic oxonium ions to find glycopeptides, by showing that a wealth of different glycopeptides can be found in a published phosphopeptide data set
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