The E3 ligase RNF34 is a novel negative regulator of the NOD1 pathway

To identify the regulator of nucleotide-binding oligomerization domain-containing protein 1 (NOD1) and its regulatory function.

We performed a yeast two-hybrid screening assay and identified the E3 ligase RNF34 as a candidate partner of NOD1. Using co-immunoprecipitation (co-IP) and glutathione S transferase (GST)-pull down assays, we further confirmed that RNF34 is associated with NOD1. Western blotting showed that RNF34 downregulated the stability of NOD1 and promoted its ubiquitination. Functional analysis demonstrated that RNF34 overexpression inhibited NOD1-dependent activation of nuclear factor-kappa B (NF-κB), whereas knockdown of RNF34 using small interfering RNA increased NF-κB activation following stimulation from NOD1 overexpression or transfection of γ-D-glutamyl-meso-diaminopimelic acid.

These findings confirm that RNF34 is a negative regulator of the NOD1 pathway through direct interaction and ubiquitination of NOD1, and suggest a novel regulatory mechanism of NOD1.