The GATA transcription factor ELT-2 modulates both the expression and methyltransferase activity of PRMT-1 in Caenorhabditis elegans.

Protein arginine methyltransferase 1 (PRMT1) catalyzes asymmetric arginine dimethylation of cellular proteins and thus modulates various biological processes, including gene regulation, RNA metabolism, cell signaling and DNA repair. Since prmt-1 null mutant completely abolishes asymmetric dimethylarginine in C. elegans, PRMT-1 is thought to play a crucial role in determining levels of asymmetric arginine dimethylation. However, the mechanism underlying the regulation of PRMT-1 activity remains largely unknown. Here, we explored for transcription factors that induce the expression of PRMT-1 by an RNAi screen using transgenic C. elegans harbouring prmt-1 promoter upstream of gfp. Of 529 clones, we identify a GATA transcription factor elt-2 as a positive regulator of Pprmt-1:: gfp expression and show that elt-2 RNAi decreases endogenous PRMT-1 expression at mRNA and protein levels. Nevertheless, surprisingly arginine methylation levels are increased when elt-2 is silenced, implying that erythroid-like transcription factor (ELT)-2 may also have ability to inhibit methyltransferase activity of PRMT-1. Supporting this idea, GST pull-down and co-immunoprecipitation assays demonstrate the interaction between ELT-2 and PRMT-1. Furthermore, we find that ELT-2 interferes with PRMT-1-induced arginine methylation in a dose-dependent manner. Collectively, our results illustrate the two modes of PRMT-1 regulation, which could determine the levels of asymmetric arginine dimethylation in C. elegans.

Asymmetric arginine dimethylation determines life span in C. elegans by regulating forkhead transcription factor DAF-16.

Arginine methylation is a widespread posttranslational modification of proteins catalyzed by a family of protein arginine methyltransferases (PRMTs). It is well established that PRMTs are implicated in various cellular processes, but their physiological roles remain unclear. Using nematodes with a loss-of-function mutation, we show that prmt-1, the major asymmetric arginine methyltransferase, is a positive regulator of longevity in C. elegans. This regulation is dependent on both its enzymatic activity and DAF-16/FoxO transcription factor, which is negatively regulated by AKT-mediated phosphorylation downstream of the DAF-2/insulin signaling. prmt-1 is also required for stress tolerance and fat storage but not dauer formation in daf-2 mutants. Biochemical analyses indicate that PRMT-1 methylates DAF-16, thereby blocking its phosphorylation by AKT. Disruption of PRMT-1 induces phosphorylation of DAF-16 with a concomitant reduction in the expression of longevity-related genes. Thus, we provide a mechanism by which asymmetric arginine dimethylation acts as an antiaging modification in C. elegans.

The C. elegans PRMT-3 possesses a type III protein arginine methyltransferase activity.

Protein arginine methylation is a common post-translational modification in eukaryotes that is catalyzed by a family of the protein arginine methyltransferases (PRMTs). PRMTs are classified into three types: type I and type II add asymmetrically and symmetrically dimethyl groups to arginine, respectively, while type III adds solely monomethyl group to arginine. However, although the enzymatic activity of type I and type II PRMTs have been reported, the substrate specificity and the methylation activity of type III PRMTs still remains unknown. Here, we report the characterization of Caenorhabditis elegans PRMT-2 and PRMT-3, both of which are highly homologous to human PRMT7. We find that these two PRMTs can bind to S-adenosyl methionine (SAM), but only PRMT-3 has methyltransferase activity for histone H2A depending on its SAM-binding domain. Importantly, thin-layer chromatographic analysis demonstrates that PRMT-3 catalyzes the formation of monomethylated, but not dimethylated arginine. Our study thus identifies the first type III PRMT in C. elegans and provides a means to elucidate the physiological significance of arginine monomethylation in multicellular organisms.

Synthesis and anti-barnacle activities of novel 3-isocyanotheonellin analogues.

An antifouling active natural compound, 3-isocyanotheonellin, and its analogues were synthesized and evaluated for antifouling activity against the larvae of the barnacle Balanus amphirite in order to explore structure-activity relationships. The anti-barnacle effect of the 3-isocyanotheonellin analogues was in the EC50 range 0.18-7.20 micrograms ml-1. Some synthesized analogues exhibited potent antifouling activity as high as 3-isocyanothoenllin, and none of the synthesized isocyano compounds showed significant toxicity. The results of the present study suggest that an isocyano group and a hydrophobic site at a suitable position are important for potent antifouling activity without toxicity.