A novel E4BP4 element drives circadian expression of mPeriod2

Period2 (Per2) is an essential component of the mammalian clock mechanism and robust circadian expression of Per2 is essential for the maintenance of circadian rhythms. Although recent studies have shown that the circadian E2 enhancer (a non-canonical E-box) accounts for most of the circadian transcriptional drive of mPer2, little is known about the other cis-elements of mPer2 oscillatory transcription. Here, we examined the contribution of E4BP4 to Per2 mRNA oscillation in the cell-autonomous clock. Knockdown experiments of E4BP4 in both Northern blots and real-time luciferase assays suggested that endogenous E4BP4 negatively regulates Per2 mRNA oscillation. Sequence analysis revealed two putative E4BP4-binding sites (termed A-site and B-site) on mammalian Per2 promoter regions. Luciferase assays with mutant constructs showed that a novel E4BP4-binding site (B-site) is responsible for E4BP4-mediated transcriptional repression of Per2. Furthermore, chromatin immunoprecipitation assays in vivo showed that the peak of E4BP4 binding to the B-site on the Per2 promoter almost matched the trough of Per2 mRNA expression. Importantly, real-time luciferase assays showed that the B-site in addition to the E2 enhancer is required for robust circadian expression of Per2 in the cell-autonomous clock. These findings indicated that E4BP4 is required for the negative regulation of mammalian circadian clocks

Mating rhythms of Drosophila: rescue of tim(01 )mutants by D. ananassae timeless

BACKGROUND: It is reported that the circadian rhythms of female mating activity differ among Drosophila species and are controlled by an endogenous circadian clock. Here, we found that the mating rhythm of D. ananassae differed from that of D. melanogaster. Moreover, to evaluate the effect of clock gene products on mating activities, we examined the mating activity of D. melanogaster timeless (tim(01)) transgenic fly harboring heat-shock promotor driven-D. ananassae timeless (tim) gene (hs-AT tim(01)). METHODS: Flies were maintained under light/dark (LD) cycles for several days and then they were transferred to constant dark (DD) conditions at 25°C. Transformant flies were heat-shocked for 30 min (PZT 10.5–11.0 or PZT 22.5–23.0; PZT means Projected Zeitgeber Time) at 37°C every day. Daily expressions of D. ananassae TIMELESS (TIM) protein in transgenic flies were measured by western blotting. To examine whether the timing of D. ananassae TIM protein induction by heat shock can change the patterns of the behavior activities of D. melanogaster tim(01 )flies, we measured locomotor and mating activity rhythms under DD at 25°C ± 0.5°C except when heat shock was applied. RESULTS: Heat shock applied at PZT 10.5–11.0 and at PZT 22.5–23.0 induced high TIM levels during subjective night and day, respectively, in hs-AT tim(01 )flies. The locomotor rhythm of these flies was changed from diurnal to nocturnal by the timing of D. ananassae TIM induction. However, the mating rhythm of these flies could not be entrained by the timing of D. ananassae TIM induction. CONCLUSION: The pattern of mating activity rhythms of D. ananassae and of D. melanogaster differed. The mating activity rhythms of D. melanogaster tim(01 )flies harboring hs-AT tim appeared after heat-shock but the pattern and phase differed from those of wild-type D. ananassae and D. melanogaster. Moreover, the mating rhythm of these flies could not be entrained by the timing of D. ananassae TIM induction although the locomotor rhythm of hs-AT tim(01 )was changed from diurnal to nocturnal according to the timing of D. ananassae TIM induction. These data suggest that species-specific mating activities require output pathways different from those responsible for locomotor rhythms

Molecular characterization of Mybbp1a as a co-repressor on the Period2 promoter

The circadian clock comprises transcriptional feedback loops of clock genes. Cryptochromes are essential components of the negative feedback loop in mammals as they inhibit CLOCK-BMAL1-mediated transcription. We purified mouse CRY1 (mCRY1) protein complexes from Sarcoma 180 cells to determine their roles in circadian gene expression and discovered that Myb-binding protein 1a (Mybbp1a) interacts with mCRY1. Mybbp1a regulates various transcription factors, but its role in circadian gene expression is unknown. We found that Mybbp1a functions as a co-repressor of Per2 expression and repressed Per2 promoter activity in reporter assays. Chromatin immunoprecipitation (ChIP) assays revealed endogenous Mybbp1a binding to the Per2 promoter that temporally matched that of mCRY1. Furthermore, Mybbp1a binding to the Per2 promoter correlated with the start of the down-regulation of Per2 expression and with the dimethylation of histone H3 Lys9, to which it could also bind. These findings suggest that Mybbp1a and mCRY1 can form complexes on the Per2 promoter that function as negative regulators of Per2 expression

Effects of vasoactive intestinal contractor (VIC) and endothelin on intracellular calcium level in neuroblastoma NG108-15 cells

AbstractEffects on [Ca2+]i levels of endothelin-1 (ET) and vasoactive intestinal contractor peptide (VIC), which is a novel member of the endothelin family, were examined in fura 2-loaded neuroblastoma NG108-15 cells. VIC was found to be a very effective stimulus for intracellular Ca2+ mobilization and to be more potent than ET. Intracellular calcium response to sequential addition of two stimulants exhibited the homologous desensitization of either ET or VIC, but no heterologous desensitization between ET and VIC. This indicates evidence suggesting that these two peptides act through distinct receptors

Clock mutation affects circadian regulation of circulating blood cells

BACKGROUND: Although the number of circulating immune cells is subject to high-amplitude circadian rhythms, the underlying mechanisms are not fully understood. METHODS: To determine whether intact CLOCK protein is required for the circadian changes in peripheral blood cells, we examined circulating white (WBC) and red (RBC) blood cells in homozygous Clock mutant mice. RESULTS: Daytime increases in total WBC and lymphocytes were suppressed and slightly phase-delayed along with plasma corticosterone levels in Clock mutant mice. The peak RBC rhythm was significantly reduced and phase-advanced in the Clock mutants. Anatomical examination revealed hemoglobin-rich, swollen red spleens in Clock mutant mice, suggesting RBC accumulation. CONCLUSION: Our results suggest that endogenous clock-regulated circadian corticosterone secretion from the adrenal gland is involved in the effect of a Clock mutation on daily profiles of circulating WBC. However, intact CLOCK seems unnecessary for generating the rhythm of corticosterone secretion in mice. Our results also suggest that CLOCK is involved in discharge of RBC from the spleen

Well-Differentiated Extraskeletal Osteosarcoma Arising from the Retroperitoneum That Recurred as Anaplastic Spindle Cell Sarcoma

Extraskeletal osteosarcoma is an uncommon high-grade malignant soft tissue sarcoma. Well-differentiated extraskeletal osteosarcoma is thought to have a better prognosis than classical extraskeletal osteosarcoma, but dedifferentiation after recurrence has also been reported. We present a case of a primary retroperitoneal extraskeletal osteosarcoma in a 62-year-old Japanese woman. Abdominal CT revealed a large mass with diffuse calcification in the right retroperitoneal space and tumor resection was performed. The histopathological diagnosis was well-differentiated retroperitoneal extraskeletal osteosarcoma. She was followed up by CT every 6 months without adjuvant radiotherapy and chemotherapy for 31 months until anaplastic high-grade spindle cell sarcoma recurred in the retroperitoneum. Our case is the seventh reported description of well-differentiated extraskeletal sarcoma, and the first to arise in the retroperitoneum and recur as an entirely dedifferentiated spindle cell sarcoma

Interferon-α suppresses hepatitis B virus enhancer II activity via the protein kinase C pathway

AbstractHBV has two enhancer (En) regions each of which promotes its own transcription. En II regulates production of pregenomic RNA, a key product of HBV replication, more strongly than En I. Although IFN-α has been found to suppress En I activity, its effect on En II activity has not been examined. Here we used luciferase assay to demonstrate that IFN-α suppresses En II activity. Analysis with several deletion/mutation constructs identified two major segments, nt 1703–1727 and nt 1746–1770, within the En II sequence as being responsible for the suppressive effects of IFN-α. Pre-treatment with protein kinase C (PKC) inhibitors blocked this effect regardless of the expression levels of phospho-STAT1 and Mx upon IFN-α stimulation. These results indicate that IFN-α suppresses En II activity via the PKC pathway, which may be an alternative suppressive pathway for HBV replication. (136 words)