Profiling of promoter occupancy by PPAR alpha in human hepatoma cells via ChIP-chip analysis
NUCLEIC ACIDS RESEARCH
Authors: van der Meer, David L. M.; Degenhardt, Tatjana; Vaisanen, Sami; de Groot, Philip J.; Heinaniemi, Merja; de Vries, Sacco C.; Muller, Michael; Carlberg, Carsten; Kersten, Sander
Abstract
The transcription factor peroxisome proliferator-activated receptor alpha (PPAR alpha) is an important regulator of hepatic lipid metabolism. While PPAR alpha is known to activate transcription of numerous genes, no comprehensive picture of PPAR alpha binding to endogenous genes has yet been reported. To fill this gap, we performed Chromatin immunoprecipitation (ChIP)-chip in combination with transcriptional profiling on HepG2 human hepatoma cells treated with the PPAR alpha agonist GW7647. We found that GW7647 increased PPAR alpha binding to 4220 binding regions. GW7647-induced binding regions showed a bias around the transcription start site and most contained a predicted PPAR binding motif. Several genes known to be regulated by PPAR alpha, such as ACOX1, SULT2A1, ACADL, CD36, IGFBP1 and G0S2, showed GW7647-induced PPAR alpha binding to their promoter. A GW7647-induced PPAR alpha-binding region was also assigned to SREBP-targets HMGCS1, HMGCR, FDFT1, SC4MOL, and LPIN1, expression of which was induced by GW7647, suggesting cross-talk between PPAR alpha and SREBP signaling. Our data furthermore demonstrate interaction between PPAR alpha and STAT transcription factors in PPAR alpha-mediated transcriptional repression, and suggest interaction between PPAR alpha and TBP, and PPAR alpha and C/EBP alpha in PPAR alpha-mediated transcriptional activation. Overall, our analysis leads to important new insights into the mechanisms and impact of transcriptional regulation by PPAR alpha in human liver and highlight the importance of cross-talk with other transcription factors.
Functional polymorphisms in inbred rat strains and their allele frequencies in commercially available outbred stocks
PHYSIOLOGICAL GENOMICS
Authors: Kuramoto, Takashi; Nakanishi, Satoshi; Serikawa, Tadao
Abstract
Polymorphisms that have been proven to influence gene functions are called functional polymorphisms. It is significant to know the distribution of functional polymorphisms in the rat, widely used in animal models for human diseases. In this study, we assessed 16 functional polymorphisms consisting of 3 coat color and 13 disease-associated genes in 136 rat strains, as a part of the genetic profiling program of the National Bio Resource Project for the Rat (NBRP-Rat). Polymorphisms of Cdkn1a, Fcgr3, Grp10, Lss, and Fdft1, which were proven to function in prostate tumorigenesis, glomerulonephritis, hyperphagia, and cholesterol biosynthesis, were shared among various inbred strains. These findings indicated that most rat strains harbored the disease-associated alleles and suggested that many unidentified functional polymorphisms might exist in inbred rat strains. The functional polymorphisms shared in inbred strains were also observed within outbred stocks available commercially. Therefore, this implies that experimental plans based on either rat inbred strains or outbred stocks need to be carefully designed with a full understanding of the genetic characteristics of the animals. To select the most suitable strains for experiments, the NBRP-Rat will periodically improve and update the genetic profiles of rat strains.