CAMP signaling regulates DNA hydroxymethylation by augmenting the intracellular labile ferrous iron pool.

Vladimir Camarena,Tyler C Huff,Sushmita Mustafi,Allegra T Aron,David W Sant,Gaofeng Wang,Paula V Monje,Christopher J Chang,Ryan K Muir,Adam R Renslo

doi:10.7554/elife.29750

Abstract

It is widely accepted that cAMP regulates gene transcription principally by activating the protein kinase A (PKA)-targeted transcription factors. Here, we show that cAMP enhances the generation of 5-hydroxymethylcytosine (5hmC) in multiple cell types. 5hmC is converted from 5-methylcytosine (5mC) by Tet methylcytosine dioxygenases, for which Fe(II) is an essential cofactor. The promotion of 5hmC was mediated by a prompt increase of the intracellular labile Fe(II) pool (LIP). cAMP enhanced the acidification of endosomes for Fe(II) release to the LIP likely through RapGEF2. The effect of cAMP on Fe(II) and 5hmC was confirmed by adenylate cyclase activators, phosphodiesterase inhibitors, and most notably by stimulation of G protein-coupled receptors (GPCR). The transcriptomic changes caused by cAMP occurred in concert with 5hmC elevation in differentially transcribed genes. Collectively, these data show a previously unrecognized regulation of gene transcription by GPCR-cAMP signaling through augmentation of the intracellular labile Fe(II) pool and DNA hydroxymethylation.

Highlights

Cyclic AMP, the second messenger, converts the binding of ligands with many different G-protein coupled receptors (GPCRs, known as seven-transmembrane domain receptors) into various biological activities (Sutherland, 1970)
CAMP exerts its function through three major targets À Cyclic AMP (cAMP)-dependent protein kinase A (PKA), cyclic nucleotide-gated ion channels (CNGCs), and exchange protein directly activated by cAMP (Epac)
Our results show a previously unknown pathway of G protein-coupled receptors (GPCR)-cAMP signaling in promoting the intracellular labile Fe(II) pool, enhancing DNA hydroxymethylation and changing gene transcription

Summary

Introduction

Cyclic AMP (cAMP), the second messenger, converts the binding of ligands with many different G-protein coupled receptors (GPCRs, known as seven-transmembrane domain receptors) into various biological activities (Sutherland, 1970). CAMP exerts its function through three major targets À cAMP-dependent protein kinase A (PKA), cyclic nucleotide-gated ion channels (CNGCs), and exchange protein directly activated by cAMP (Epac). It is well known that cAMP has an impact on gene transcription, which is currently considered to be mediated by the PKA-targeted. Three transcription factors, including cAMP response element-binding protein (CREB), cAMP response element modulator (CREM), and activating transcription factor 1 (ATF1), can be phosphorylated by PKA and subsequently bind to cAMP response elements (CRE) in gene promoters, generally to activate gene transcription (Sands and Palmer, 2008)

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