Structure and function of the enhancer 3'' to the human A gamma globin gene.

An enhancer is located immediately 3' to the A gamma globin gene. We have used DNase I footprinting to map the sites of interaction of nuclear proteins with the DNA sequences of this enhancer. Eight footprints were discovered, distributed over 600 base pairs of DNA. Three of these contain a consensus binding site for the erythroid specific factor GATA-I. Each of these GATA-1 sites had an enhancer activity when inserted into a reporter plasmid and tested in human erythroleukemia cells. Other footprints within the enhancer contained consensus binding sequences for the ubiquitous, positive regulatory proteins AP2 and CBP-1. An Sp1-like recognition sequence was also identified. Synthetic oligonucleotides encompassing two of the footprints generated a slowly migrating complex in gel mobility shift assays. The same complex forms on a fragment of the human gamma globin gene promoter extending from -260 to -200. The DNaseI footprint of this protein complex with the enhancer overlapped a sequence, AGGAGGA, found within the binding site for a protein that interacts with the chicken beta globin promoter and enhancer, termed the stage selector element. We propose that this complex of proteins may be involved in the human gamma globin promoter-enhancer interaction.     

The kinase MSK1 is required for induction of c-<Emphasis Type="Italic">fos</Emphasis> by lysophosphatidic acid in mouse embryonic stem cells

Background

The regulation of the immediate-early gene c-fos serves as a paradigm for signal-activated gene induction. Lysophosphatidic acid is a potent serum-borne mitogen able to induce c-fos.

Results

Analysing the signalling events following stimulation of mouse embryonic stem cells with serum and lysophosphatidic acid, we show that the extracellular signal-regulated kinase (ERK) pathway is involved in mediating c-fos induction. We demonstrate that the ERK-activated kinase MSK1 is required for full c-fos promoter activation, as well as for the phosphorylation of cAMP-responsive element (CRE) binding proteins. We propose that MSK1 contributes to ERK-mediated c-fos promoter activation by targeting CRE binding proteins.

Conclusion

These results show that MSK1 is an important ERK-activated mediator of mitogen-stimulated c-fos induction. In addition, they indicate that MSK1 could act through CRE binding proteins to achieve c-fos promoter activation. Thus, they further our understanding of the complex regulation of the model immediate-early gene c-fos.

     

Monitoring immediate-early gene expression through firefly luciferase imaging of HRS/J hairless mice

Background  

Gene promoters fused to the firefly luciferase gene (luc) are useful for examining gene regulation in live transgenic mice and they provide unique views of functioning organs. The dynamics of gene expression in cells and tissues expressing luciferase can be observed by imaging this enzyme's bioluminescent oxidation of luciferin. Neural pathways involved in specific behaviors have been identified by localizing expression of immediate-early genes such as c-fos. A transgenic mouse line with luc controlled by the human c-fos promoter (fos::luc) has enabled gene expression imaging in brain slice cultures. To optimize imaging of immediate-early gene expression throughout intact mice, the present study examined fos::luc mice and a second transgenic mouse containing luc controlled by the human cytomegalovirus immediate-early gene 1 promoter and enhancer (CMV::luc). Because skin pigments and hair can significantly scatter light from underlying structures, the two transgenic lines were crossed with a hairless albino mouse (HRS/J) to explore which deep structures could be imaged. Furthermore, live anesthetized mice were compared with overdosed mice.