Search

J. Neurochem. (2011) 119, 6-17. Abstract Arylalkylamine N-acetyltransferase (AANAT) is the key regulatory enzyme controlling the daily rhythm of melatonin biosynthesis. In chicken retinal photoreceptor cells, Aanat transcription and AANAT activity are regulated in part by cAMP-dependent mechanisms. The purpose of this study was to identify regulatory elements within the chicken Aanat promoter responsible for cAMP-dependent induction. Photoreceptor-enriched retinal cell cultures were transfected with a luciferase reporter construct containing up to 4 kb of 5′-flanking region and the first exon of Aanat. Forskolin treatment stimulated luciferase activity driven by the ∼4 kb promoter construct and by all 5′-deletion constructs except the smallest, Aanat (−217 to +120)luc. Maximal basal and forskolin-stimulated expression levels were generated by the Aanat (−484 to +120)luc construct. This construct lacks a canonical cyclic AMP-response element (CRE), but contains two other potentially important elements in its sequence: an eight times TTATT repeat (TTATT8) and a CRE-like sequence. Electrophoretic mobility shift assays, luciferase reporter assays, chromatin immunoprecipitation, and siRNA experiments provide evidence that these elements bind c-Fos, JunD, and CREB to enhance basal and forskolin-stimulated Aanat transcription. We propose that the CRE-like sequence and TTATT8 elements in the 484 bp proximal promoter interact to mediate cAMP-dependent transcriptional regulation of Aanat. [ABSTRACT FROM AUTHOR]

Abstract: Myocyte stress 1 (MS1) is a recently described striated muscle actin-binding protein that is up-regulated in the early stages of pressure overload left ventricular hypertrophy. The aim of this study was to determine whether MS1 induces cellular hypertrophy and protects against apoptosis. Over-expressed MS1 co-localized with actin in H9c2 cells and altered expression of genes of the myocardin-related transcription factor (MRTF)/serum response factor (SRF) transcriptional pathways and in addition the apoptosis repressor with caspase recruitment domain (Nol3) gene. The size of cells over-expressing MS1 was significantly increased by 55% and over-expression of MS1 dramatically inhibited staurosporine-induced apoptosis by 89%. These findings suggest the involvement of MS1 in cellular hypertrophy and protection against apoptosis. [Copyright &y& Elsevier]

Abstract: Increased plasminogen activator inhibitor-1 (PAI-1) activity is associated with greater risk of myocardial infarction. PAI-1 expression is regulated by a 4G/5G promoter polymorphism. The 4G allele is associated with higher PAI-levels and greater circadian variation. Here we show that clock protein heterodimers BMAL/CLOCK cause greater activation (≈2-fold, P <0.05) of the 4G allele. Site-directed mutagenesis studies suggest that clock genes act on two canonical E-boxes to regulate PAI-1 promoter activity. These results identify a potential novel mechanism whereby allele-specific clock genes – mediated modulation of PAI-1 expression may contribute to circadian variation in cardiac risk. [Copyright &y& Elsevier]

Abstract The molecular core of the vertebrate circadian clock is a set of clock genes, whose products interact to control circadian changes in physiology. These clock genes are expressed in all tissues known to possess an endogenous self-sustaining clock, and many are also found in peripheral tissues. In the present study, the expression patterns of two clock genes, cBmal1 and cMOP4, were examined in the chicken, a useful model for analysis of the avian circadian system. In two tissues which contain endogenous clocks – the pineal gland and retina – circadian fluctuations of both cBmal1 and cMOP4 mRNAs were observed to be synchronous; highest levels occurred at Zeitgeber time 12. Expression of these genes is also rhythmic in several peripheral tissues; however, the phases of these rhythms differ from those in the pineal gland and retina: in the liver the peaks of cMOP4 and cBmal1 mRNAs are delayed 4–8 h and in the heart they are advanced by 4 h, relative to those in the pineal gland and retina. These results provide the first temporal characterization of cBmal1 and cMOP4 mRNAs in avian tissues: their presence in avian peripheral tissues indicates they may influence temporal features of daily rhythms in biochemical, physiological, and behavioral functions at these sites. [ABSTRACT FROM AUTHOR]

We have identified and characterised a cDNA encoding a novel gene, designated myocyte stress 1 (ms1), that is up-regulated within 1 h in the left ventricle following the application of pressure overload by aortic banding in the rat. The deduced ms1 protein of 317 amino acids contains several putative functional motifs, including a region that is evolutionarily conserved. Distribution analysis indicates that rat ms1 mRNA expression is predominantly expressed in striated muscle and progressively increases in the left ventricle from embryo to adulthood. These findings suggest that ms1 may be important in striated muscle biology and the development of pressure-induced left ventricular hypertrophy. [Copyright &y& Elsevier]

We have identified and characterized an ortholog of the putative mammalian clock gene cryptochrome 2 (Cry2) in the chicken, Gallus domesticus. Northern blot analysis of gCry2 mRNA indicates widespread distribution in central nervous and peripheral tissues, with very high expression in pineal and retina. In situ hybridization of chick brain and retina reveals expression in photoreceptors and in visual and circadian system structures. Expression is rhythmic; mRNA levels predominate in late subjective night. The present data suggests that gCry2 is a candidate avian clock gene and/or photopigment and set the stage for functional studies of gCry2. [Copyright &y& Elsevier]