The S promoter of hepatitis B virus is regulated by positive and negative elements.

The S promoter, one of the major hepatitis B virus (HBV) promoters, directs the synthesis of mRNA for surface antigen. Transient expression studies revealed that this promoter is highly active in the Alexander hepatoma cell line but not in SK-Hep1 and HeLa cells. We found that a distal element of the promoter (-103 to -48) confers this cell-type-specific behavior through a mechanism in which the promoter activity is repressed in HeLa and SK-Hep1 cells but increased in Alexander cells. By using an inhibitor of protein synthesis, we obtained evidence that a labile repressor(s) confers the negative effect in SK-Hep1 cells. We also found an enhancerlike activity associated with a small DNA segment of the S promoter (-27 to + 30). This proximal element was active in HeLa and SK-Hep1 cells only in the absence of the distal negative element. Finally, analysis of S promoter deletion mutants demonstrated that the -27 to -17 region of the S promoter is crucial for its activity.     

Identification of negative and positive regulatory elements in the human renin gene

Renin gene expression is tissue-specific and under complex hormonal control. To investigate which DNA elements are involved in the control of human renin gene expression, we performed transient DNA transfer experiments with renin-chloramphenicol acetyltransferase fusions. We have mapped a complex arrangement of positive and negative control sequences in the 5' flanking region of the human renin gene. One positive control element is active in either orientation and defines a renin gene enhancer. The negative element is also active in either orientation and defines a renin gene silencer. Mapping in the same region as the silencer is a cAMP-responsive element, a sequence conserved in mouse, rat, and human renin genes.     

Lysozyme gene activity in chicken macrophages is controlled by positive and negative regulatory elements.

The chicken lysozyme gene is constitutively active in macrophages and under the control of steroid hormones in the oviduct. To investigate which DNA elements are involved in the control of its expression in macrophages we performed transient DNA transfer experiments with two different types of plasmids: 5'-deletion mutants of the upstream region of the chicken lysozyme gene and different fragments from this area in front of the thymidine kinase promoter (herpes simplex virus), each placed in front of the CAT (chloramphenicol acetyl transferase) coding sequence. Two enhancers (E-2.7 kb and E-0.2 kb) were characterized. They are active in macrophages, but not in chicken fibroblasts. Furthermore a negative element (N-2.4 kb) was identified, which is active in fibroblasts and promyelocytes, but not in mature macrophages. The combined action of all three elements contributes to the observed lysozyme gene activities: no activity in fibroblasts, moderate activity in promyelocytes and high activity in mature macrophages.     

The human PER1 gene is transcriptionally regulated by multiple signaling pathways

The mammalian period (Per) genes are components of the circadian clock and appear to be regulated via an autoregulatory feedback loop. Here we show that the human PER1 (hPER1) gene is synergistically activated by protein kinases A and C (PKA, PKC) and cAMP responsive element binding protein. Activators and inhibitors of PKA as well as PKC modulate endogenous hPER1 expression and hPER1 promoter-driven reporter gene activity in a dose-dependent manner. Our results suggest that the hPER1 promoter acts as a sensor for multiple signaling molecules thereby integrating different physiological parameters. This regulation of hPER1 appears to be significant for rapid adaptation to changing environmental conditions.     

The gene for human apolipoprotein CI is located 4.3 kilobases away from the apolipoprotein E gene on chromosome 19

Summary We have isolated a cDNA clone for apolipoprotein CI and a genomic clone for apolipoprotein E, and by hybridisation and mapping experiments found the gene for apoCI to be located on the genomic apoE clone. The distance between the loci was 4.3 kb.     

Expression of the cyclin-dependent kinase inhibitor Dacapo is regulated by cyclin E

The Cip/Kip family of cyclin-dependent kinase inhibitors (CKIs) has been implicated in mediating cell cycle arrest prior to terminal differentiation. In many instances, increased expression of CKIs immediately precedes mitotic arrest. However, the mechanism that activates CKI expression in cells that are about to stop dividing has remained elusive. Here we have addressed this issue by investigating the expression pattern of dacapo, a Cip/Kip CKI in Drosophila. We show that the accumulation of dacapo RNA and protein requires Cyclin E and that increased expression of Cyclin E can induce dacapo expression. We also show that the oscillation of the Cyclin E and Dacapo proteins are tightly coupled during ovarian endocycles. Our results argue for a mechanism where Cyclin E/Cdk activity induces Dacapo expression but only within certain windows that are permissive for dacapo expression.