The world's first wiki where authorship really matters (Nature Genetics, 2008). Due credit and reputation for authors. Imagine a global collaborative knowledge base for original thoughts. Search thousands of articles and collaborate with scientists around the globe.

wikigene or wiki gene protein drug chemical gene disease author authorship tracking collaborative publishing evolutionary knowledge reputation system wiki2.0 global collaboration genes proteins drugs chemicals diseases compound
Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)
 
 
 
 
 

Cloning and functional analysis of spliced isoforms of human nuclear factor I-X: interference with transcriptional activation by NFI/ CTF in a cell-type specific manner.

Previous studies of the epithelial specificity of the human papillomavirus type 16 (HPV-16) enhancer pointed out an important role of nuclear factor I (NFI). In epithelial cells, NFI proteins are derived from the NFI-C gene and referred to as NFI/ CTF. In contrast, fibroblasts, where the enhancer is inactive, express high levels of NFI from the NFI-X gene. To compare NFI-C and NFI-X derived transcription factors, we cloned and functionally investigated two differentially spliced forms of NFI-X from human fibroblasts. NFI-X1 has 95% homology with a transcript previously identified in hamster liver cells. NFI-X2, a spliced variant, misses 41 amino acids of the proline-rich activation domain. NFI-X expression, examined by Northern blots, shows strong cell-type specific variation in comparison with NFI/ CTF. While the transcriptional activation domain of NFI-X2, functionally tested as GAL4-fusion protein in epithelial and fibroblast cells, activates transcription from promoter as well as enhancer position similar to NFI/CTF-1, the activation domain of NFI-X1 fails to activate transcription from enhancer position. In Drosophila cells, void of endogenous NFI proteins, full length NFI/CTF-1 and NFI-X2 activate a reporter construct containing only NFI sites as well as the NFI dependent HPV-16 enhancer. In contrast, NFI-X1 fails to activate the HPV-16 enhancer. Furthermore, overexpression of NFI-X1 in epithelial cells down-regulates the HPV-16 enhancer. Our findings suggest that the family of NFI transcription factors should not be viewed as constitutive activators, but rather, that NFI-C and NFI-X have divergent functions after binding in promoter or enhancer position. This property, combined with the differential expression of NFI-X, can achieve cell-type specificity of NFI dependent promoters and enhancers.[1]

References

 
WikiGenes - Universities