APEX1 regulation of aldosterone synthase gene transcription is disrupted by a common polymorphism in humans.
BACKGROUND
The genetic mechanisms underlying hypertension are unclear, but relative aldosterone excess, present in ≈10% of hypertensive patients, is known to be a heritable trait. This phenotype associates with a T/C single nucleotide polymorphism (SNP) at position -344 of the aldosterone synthase gene (CYP11B2). However, deletion of this SNP has no effect on gene transcription. We have identified another T/C SNP at -1651, in tight linkage disequilibrium with the -344 SNP and here investigate its functional effect on CYP11B2 transcription.


OBJECTIVE
We assessed the effect on transcriptional activity of the -1651 T/C SNP in vivo and in vitro and propose the mechanism by which transcriptional activity is altered.


RESULTS
We demonstrated that the SNP at -1651 exerts significant allele-dependent effects on CYP11B2 transcription. We confirm binding of the transcriptional repressor APEX1 to -1651T, which is associated with reduced transcriptional activity in relation to the less strongly bound -1651C. We show that inhibiting APEX1 by small molecule inhibition or small interfering RNA (SiRNA) leads to increased CYP11B2 transcription. In addition, overexpression of APEX1 is associated with reduced transcriptional activity. Finally, we also show that -1651T associates with lower excretion rates of aldosterone metabolites in human subjects.


CONCLUSIONS
We conclude that APEX1 is a novel transcriptional repressor of CYP11B2 and that differential APEX1 binding at -1651 of CYP11B2 results in altered gene expression. This mechanism may contribute to the observed relationship between CYP11B2 genotype and aldosterone phenotype in a subgroup of hypertensive patients.
Institute of Cardiovascular and Medical Sciences, University of Glasgow, UK. Frances.McManus@Glasgow.ac.uk
Frances
F
McManus
William
W
Sands
Louise
L
Diver
Scott M
SM
MacKenzie
Robert
R
Fraser
Eleanor
E
Davies
John M
JM
Connell
D000328:Adult; D000368:Aged; D019405:Cytochrome P-450 CYP11B2 / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics*; D004260:DNA Repair / Q000235:genetics; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000037:antagonists & inhibitors* / Q000502:physiology*; D015536:Down-Regulation / Q000235:genetics; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D020641:Polymorphism, Single Nucleotide / Q000235:genetics*; D011485:Protein Binding / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000235:genetics*; D015854:Up-Regulation / Q000235:genetics
D034741:RNA, Small Interfering; D019405:Cytochrome P-450 CYP11B2; C085108:APEX1 protein, human; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase