Sumoylation of Arabidopsis heat shock factor A2 (HsfA2) modifies its activity during acquired thermotholerance

Abstract

Post-translational modification of target proteins by the small ubiquitin-like modifier protein (SUMO) regulate many cellular processes. In this work we show SUMOylation of the heat shock transcription factor, AtHsfA2, in connection with the plant's response to heat stress and acquired thermotolerance. Using the Yeast two hybrid and the bimolecular fluorescence complementation system, we have found that AtSUMO1 physically interacts with AtHsfA2. Further investigation allowed us to determine that Lys 315 of AtHsfA2 is the main SUMOylation site. Overexpression of AtSUMO1 led to a decrease in AtHsfA2 transcriptional activation of heat shock promoters. We have examined the effect of AtSUMO1 on AtHsfA2 during heat shock treatments. The phenotype of seedlings overexpressing AtSUMO1 resembled the phenotype of AtHsfA2 knock out seedlings, which were more sensitive than wild type seedlings to repeated heat treatment. Furthermore, AtSUMO1 overexpressing seedlings exhibited lower expression levels of small heat shock proteins as compared with wild type seedlings after heat treatment. Based on our findings, we suggest that AtSUMO1 is involved in the regulation of AtHsfA2 in acquired thermotolerance.

Quantitative Proteomics Reveals Factors Regulating RNA Biology as Dynamic Targets of Stress-induced SUMOylation in Arabidopsis

“…Notable examples were the RNA splicing/degrading/helicase proteins RSP35, RSP41, PRH75, U2AF65A, SDN3, STA1, and NUC-L1; the RNA binding proteins LA1 and CCR2; and the RNAdependent DNA methylation-related protein IDN2. Non-RNArelated factors experiencing strong increases in SUMOylation state (Ͼ7-fold) after heat stress included the heat shock transcription factor HSF2A, a previously identified SUMO target known to be important for establishing long-term acquired thermotolerance (27,41,55). Also among the Tier 1 targets was an Arabidopsis ortholog of the mammalian SIM-containing DNA gyrase MORC involved in heterochromatin condensation and transcriptional repression (56,57), the POLD3 DNA polymerase core subunit, and the histone-binding protein NRP1.…”

“…Prior studies with related HSFs in mammalian cells showed that their heat-shock-stimulated SUMOylation affects binding to their cognate promoter elements, although the direction of the response remains in question (71)(72)(73). Given the role of HSFA2 in the establishment of acquired thermotolerance, it is tempting to speculate that its SUMOylation not only is involved in basal stress tolerance (7,28), but also serves as a guard against future insults (27).…”

SUMOylation by a Stress-Specific Small Ubiquitin-Like Modifier E2 Conjugase Is Essential for Survival ofChlamydomonas reinhardtiiunder Stress Conditions

“…In Arabidopsis, HSFA2 is targeted for SUMOylation during extended exposure to heat stress and recovery (Cohen-Peer et al, 2010). In this case, SUMOylation negatively regulates the activity of this transcription factor.…”

Plant Abiotic Stress: Insights from the Genomics Era

“…AtHsfA2 also plays an important role in linking heat shock with oxidative stress signals . A recent study (Cohen-Peer et al, 2010) has demonstrated AtSUMO1 of AtHsfA2 to be involved with the plant's regulatory response to heat stress and acquired thermotolerance. Post-translational modification of target proteins by SUMO proteins (see cold section for background) regulates many cellular processes, and adds a further layer to this complex network In a recent study to identify potential regulatory components involved in thermotolerance, a reverse genetics approach was used by screening Arabidopsis T-DNA insertion mutants for lines displaying phenotypic decreased thermotolerance.…”