Transcriptional Activation of Low-Density Lipoprotein Receptor Gene by DJ-1 and Effect of DJ-1 on Cholesterol Homeostasis

DJ-1 is a novel oncogene and also causative gene for familial Parkinson’s disease park7. DJ-1 has multiple functions that include transcriptional regulation, anti-oxidative reaction and chaperone and mitochondrial regulation. For transcriptional regulation, DJ-1 acts as a coactivator that binds to various transcription factors, resulting in stimulation or repression of the expression of their target genes. In this study, we found the low-density lipoprotein receptor (LDLR) gene is a transcriptional target gene for DJ-1. Reduced expression of LDLR mRNA and protein was observed in DJ-1-knockdown cells and DJ-1-knockout mice and this occurred at the transcription level. Reporter gene assays using various deletion and point mutations of the LDLR promoter showed that DJ-1 stimulated promoter activity by binding to the sterol regulatory element (SRE) with sterol regulatory element binding protein (SREBP) and that stimulating activity of DJ-1 toward LDLR promoter activity was enhanced by oxidation of DJ-1. Chromatin immunoprecipitation, gel-mobility shift and co-immunoprecipitation assays showed that DJ-1 made a complex with SREBP on the SRE. Furthermore, it was found that serum LDL cholesterol level was increased in DJ-1-knockout male, but not female, mice and that the increased serum LDL cholesterol level in DJ-1-knockout male mice was cancelled by administration with estrogen, suggesting that estrogen compensates the increased level of serum LDL cholesterol in DJ-1-knockout female mice. This is the first report that DJ-1 participates in metabolism of fatty acid synthesis through transcriptional regulation of the LDLR gene

The Brf and TATA-binding protein subunits of the RNA polymerase III transcription factor IIIB mediate position-specific integration of the gypsy-like element, Ty3.

Ty3 integrates into the transcription initiation sites of genes transcribed by RNA polymerase III. It is known that transcription factors (TF) IIIB and IIIC are important for recruiting Ty3 to its sites of integration upstream of tRNA genes, but that RNA polymerase III is not required. In order to investigate the respective roles of TFIIIB and TFIIIC, we have developed an in vitro integration assay in which Ty3 is targeted to the U6 small nuclear RNA gene, SNR6. Because TFIIIB can bind to the TATA box upstream of the U6 gene through contacts mediated by TATA-binding protein (TBP), TFIIIC is dispensable for in vitro transcription. Thus, this system offers an opportunity to test the role of TFIIIB independent of a requirement of TFIIIC. We demonstrate that the recombinant Brf and TBP subunits of TFIIIB, which interact over the SNR6 TATA box, direct integration at the SNR6 transcription initiation site in the absence of detectable TFIIIC or TFIIIB subunit B". These findings suggest that the minimal requirements for pol III transcription and Ty3 integration are very similar