The intronic region of Fbxl12 functions as an alternative promoter regulated by UV irradiation

The ubiquitin ligases, SCF complexes, consist of Cul1, Skp1, Rbx1 and the substrate recognition components F-box proteins. Previous studies have reported that one of these F-box proteins, Fbl12, which is produced by Fbxl12 gene, regulates both cell cycle and differentiation. In this paper, we show that the intronic region of Fbxl12 gene acts as an alternative promoter and induces expression of a short form of Fbl12 that lacks F-box domain (Fbl12ΔF). We also found that UV irradiation increases Fbl12ΔF mRNA in cells. Finally, Fbl12ΔF may promote the subcellular localization of Fbl12 from nucleus to cytoplasm through their binding. Our data provide the possibility that Fbl12ΔF induced by alternative promoter controls the SCF^Fbl12 activity in response to UV stimulation.     

Regulation of PTEN transcription by p53.

PTEN tumor suppressor is frequently mutated in human cancers and is a negative regulator of PI3'K/PKB/Akt-dependent cellular survival. Investigation of the human genomic PTEN locus revealed a p53 binding element directly upstream of the PTEN gene. Deletion and mutation analyses showed that this element is necessary for inducible transactivation of PTEN by p53. A p53-independent element controlling constitutive expression of PTEN was also identified. In contrast to p53 mutant cell lines, induction of p53 in primary and tumor cell lines with wild-type p53 increased PTEN mRNA levels. PTEN was required for p53-mediated apoptosis in immortalized mouse embryonic fibroblasts. Our results reveal a unique role for p53 in regulation of cellular survival and an interesting connection in tumor suppressor signaling.     

Autoregulation of mouse BMP-2 gene transcription is directed by the proximal promoter element

The prion proteins (PrP) from sheep and mouse were produced in large quantities of full-length protein in Escherichia coli after fusion with a carboxy-terminal hexahistidine sequence. Both recombinant proteins were recognized, at variable levels, in ELISA using a panel of antibodies recognizing different parts of the PrP molecules, from the octo-repeat region (79-92 human sequence), to the C terminal end of the protein. We show that these recombinant proteins enable polyclonal antisera to be produced in PrP0/0 mice, the sheep prion protein being strongly immunogenic, using either native or guanidium hydrochloride-treated recombinant protein. Sera produced against the sheep protein also reacted in Western blot with bovine, ovine, and murine PrP res, but showed higher reactivity with sheep PrP res. Interestingly, when compared to an antiserum produced against bovine 106-121 peptidic sequence (RB1), we found strikingly different ratios of the PrP res glycoforms, in both cattle with BSE and sheep with natural scrapie, but not in scrapie infected mice. Such results further demonstrate that the assessment of PrP res glycoform ratios, using different antibodies, may depend on antibodies species-specificities.