14-3-3 binding motif phosphorylation disrupts Hdac4 organized condensates to stimulate cardiacreprogramming

Abstract

Cell fate conversion is associated with extensive epigenetic and post translational modifications (PTMs) and architectural changes of sub-organelles and organelles, yet how these events are interconnected remains unknown. We report here the identification of a phosphorylation code in 14-3-3 binding motifs (PC14-3-3) that greatly stimulates induced cardiomyocyte (iCM) formation from fibroblasts. PC14-3-3 was identified in pivotal functional proteins for iCM reprogramming, including transcription factors and epigenetic factors. Akt1 kinase and PP2A phosphatase were a key writer and eraser of the PC14-3-3 code, respectively. PC14-3-3 activation induces iCM formation with the presence of only Tbx5. In contrast, PC14-3-3 inhibition by mutagenesis or inhibitor-mediated code removal abolished reprogramming. We discovered that key PC14-3-3 embedded factors, such as Hdac4, Mef2c, Nrip1, and Foxo1, formed Hdac4 organized inhibitory nuclear condensates. Notably, PC14-3-3 activation disrupted Hdac4 condensates to promote cardiac gene expression. Our study suggests that sub-organelle dynamics regulated by a post-translational modification code could be a general mechanism for stimulating cell reprogramming and organ regeneration. HighlightsO_LIA PC14-3-3 (phosphorylation code in 14-3-3 binding motifs) is identified in pivotal functional proteins, such as HDAC4 and Mef2c, that stimulates iCM formation. C_LIO_LIAkt1 kinase and PP2A phosphatase are a key writer and a key eraser of the PC14-3-3 code, respectively, and PC14-3-3 code activation can replace Mef2c and Gata4 in cardiac reprogramming. C_LIO_LIPC14-3-3 activation disrupts Hdac4 organized condensates which results in releasing multiple 14-3-3 motif embedded proteins from the condensates to stimulate cardiac reprogramming. C_LIO_LISub-organelle dynamics and function regulated by a post-translational modification code could be a general mechanism in stimulating cell reprogramming and organ regeneration. C_LI Graphic abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=150 SRC="FIGDIR/small/567913v1_ufig1.gif" ALT="Figure 1"> View larger version (52K): org.highwire.dtl.DTLVardef@1fec3aforg.highwire.dtl.DTLVardef@e13b16org.highwire.dtl.DTLVardef@ee354borg.highwire.dtl.DTLVardef@ecd58e_HPS_FORMAT_FIGEXP M_FIG C_FIG