Since cubilin monoallelic expression was unaltered by 5Aza and TSA treatments, we concluded that the in creased cubilin mRNA levels were due to effects of these agents on the transcriptionally active cubilin allele. Both histone deacetylation and DNA methylation are associ ated with PPAR repression. In fact, HDAC1 and 3 are known selleck catalog PPAR�� co repressors. Conversely, PPAR co activators, such as CBP/p300 and SRC 1, possess histone acetylase activity required for chromatin remodel ing to allow PPAR mediated transcription. Furthermore, recent findings show that the cubilin coreceptor, megalin, is a PPAR responsive gene and its expression is augmented through inhibition of histone deacetylation. In light of these studies, we recog nized the possibility that the observed effects of TSA and 5Aza on cubilin might also involve PPAR induction.
This led us to discover that the observed effects of 5Aza and TSA on cubilin expression were dependent on PPAR and induction. Specifically, we showed that cubilin was a PPAR and responsive gene, that the expression of PPAR and was inducible by 5Aza and TSA alone, Inhibitors,Modulators,Libraries and that the effects of TSA and 5Aza on cubilin expression were dependent on increased expression of PPAR and. Similarly, we showed that TSA and 5Aza induced megalin expression was dependent on increased expression of PPAR and. While TSA and 5Aza treatments augmented PPAR and cubilin mRNA levels, Inhibitors,Modulators,Libraries no significant increase in cubilin levels was achieved by overexpressing PPAR in the absence of PPAR agonist. Therefore, the effects of TSA and 5Aza on cubilin mRNA levels cannot be attrib uted to increased PPAR mRNA levels alone.
We in ferred that, in addition to increasing Inhibitors,Modulators,Libraries PPAR expression, 5Aza and TSA treatments must also lead to PPAR acti vation. The underlying mechanism for the apparent agonist independent effects of TSA on induction of PPAR dependent transcription of cubilin Inhibitors,Modulators,Libraries remains to be established. TSA and/or 5Aza might augment levels of endogenous PPAR agonists, cause demethylation of sites on the cubilin gene, or reduce histone occupancy of the cubilin promoter. Any of these effects might be sufficient for promoting PPAR action in an agonist independent manner. Since HDACs are Inhibitors,Modulators,Libraries known co repressors and HATs are co activators of PPARs, it is reasonable to expect that inhibiting HDAC activity will shift PPARs towards a more active state. In fact, HDAC inhibitors have been reported to act as atypical PPAR agonists and studies have shown that inhib ition of HDACs stimulates transcription of PPAR responsive genes. Therefore, it is likely that in creased acetylation of histones associated with the cubilin promoter in response to HDAC inhibitor treat ment is sufficient to www.selleckchem.com/products/epz-5676.html promote PPAR driven cubilin expression.