Abstract We137: PGC-1α-dependent transcriptional regulatory mechanisms for tricarboxylic acid cycle genes in the heart.

Abstract

Many metabolic genes, including tricarboxylic acid (TCA) cycle genes, are downregulated in heart failure, which may promote the pathology due to insufficient energy production. To clarify how TCA cycle genes are downregulated in the failing heart, it is a prerequisite to clarify how these genes are transcribed in the normal heart. PGC-1α is a transcriptional co-activator that broadly induces metabolic genes through activation of transcription factors, such as ERR, Nrf1, Gabpa and YY1. Here we show that PGC-1α transcribes 13 among 14 TCA cycle genes partly through ERR, Nrf1, Gabpa and YY1. Thirteen TCA cycle genes, except for Suclg2, were downregulated in cardiac specific PGC-1α knockout (KO) mice (Relative mRNA levels in KO mice compared to wild type (WT) were CS 0.66*, Aco2 0.64*, Idh3a 0.62*, Idh3b 0.54*, Idh3g 0.54*, Ogdh 0.64*, Suclg1 0.45*, Suclg2: 1.1, Sdha 0.57*, Sdhb 0.53*, Sdhc 0.72*, Sdhd 0.57*, Fh1 0.32* and Mdh2 0.54*,p<0.05 vs. WT). ChIP-sequencing with PGC-1α antibody demonstrated that PGC-1α is localized at the promoter of thirteen TCA cycle genes, besides Suclg2. Bioinformatics analyses identified consensus binding sequences of ERR, Nrf1, Gabpa and YY1 in these promoters. Gene expression analyses with knockdown of these transcription factors demonstrated that a transcription factor whose binding sequence is found proximal to the PGC-1α localization peak transcribes the downstream genes in general. These transcription factor binding sequences were well conserved between mice and humans. ERR-, Nrf1- and Gabpa-dependent PGC-1α recruitment was verified with in vitro DNA binding assays using endogenous promoter sequences of Idh3a, Idh3g and Sdha. Taken together, this study clarifies a precise transcriptional mechanism for TCA cycle genes in the normal heart, which could be useful for understanding how those genes are dysregulated in the failing heart.