Noncanonical mono(ADP-ribosyl)ation of zinc finger SZF proteins counteracts ubiquitination for protein homeostasis in plant immunity.
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Protein ADP-ribosylation is a reversible post-translational modification that transfers ADP-ribose from NAD+ onto acceptor proteins. Poly(ADP-ribosyl)ation (PARylation), catalyzed by poly(ADP-ribose) polymerases (PARPs) and poly(ADP-ribose) glycohydrolases (PARGs), which remove the modification, regulates diverse cellular processes. However, the chemistry and physiological functions of mono(ADP-ribosyl)ation (MARylation) remain elusive. Here, we report that Arabidopsis zinc finger proteins SZF1 and SZF2, key regulators of immune gene expression, are MARylated by the noncanonical ADP-ribosyltransferase SRO2. Immune elicitation promotes MARylation of SZF1/SZF2 via dissociation from PARG1, which has an unconventional activity in hydrolyzing both poly(ADP-ribose) and mono(ADP-ribose) from acceptor proteins. MARylation antagonizes polyubiquitination of SZF1 mediated by the SH3 domain-containing proteins SH3P1/SH3P2, thereby stabilizing SZF1 proteins. Our study uncovers a noncanonical ADP-ribosyltransferase mediating MARylation of immune regulators and underpins the molecular mechanism of maintaining protein homeostasis by the counter-regulation of ADP-ribosylation and polyubiquitination to ensure proper immune responses.
author list (cited authors)
Kong, L., Feng, B., Yan, Y., Zhang, C., Kim, J. H., Xu, L., ... He, P.
complete list of authors
Kong, Liang||Feng, Baomin||Yan, Yan||Zhang, Chao||Kim, Jun Hyeok||Xu, Lahong||Rack, Johannes Gregor Matthias||Wang, Ying||Jang, Jyan-Chyun||Ahel, Ivan||Shan, Libo||He, Ping