Moyamoya Disease-Associated RNF213 Alleles Encode Dominant Negative Alleles That Globally Impair Ubiquitylation

Single nucleotide polymorphisms (SNPs) in RNF213, which encodes a 591kDa protein with AAA+ ATPase and RING E3 domains, are associated with a rare, autosomal dominant cerebrovascular disorder, Moyamoya disease (MMD). MMD-associated SNPs primarily localize to the C-terminal region of RNF213, and some affect conserved residues in the RING domain. Although the autosomal dominant inheritance of MMD could most easily be explained by RNF213 gain-of-function, the type of ubiquitylation catalyzed by RNF213 and the effects of MMD-associated SNPs on its E3-ligase activity have remained unclear. We found that the RING domain of RNF213 uses the E2-conjugating enzyme UBE2D2 to catalyze predominantly K6-dependent poly-ubiquitination events comprising a mixture of typical and atypical ubiquitin linkages. MMD-associated SNPs encode proteins with decreased E3-ligase activity and the most frequent MMD allele, RNF213R4810K, is a dominant negative mutant that decreases ubiquitylation globally. By contrast, MMD-associated RNF213 SNPs do not affect ATPase activity. We propose that decreased RNF213 E3-ligase activity is central to MMD pathogenesis.