GSE138019
Decapping enzyme NUDT12 partners with BLMH for cytoplasmic surveillance of NAD-capped RNAs
RNA polymerase II transcripts receive a protective 5' m7G cap early during transcription. An alternative cap can be acquired when RNA pol II initiation uses the redox cofactor nicotinamide adenine dinucleotide (NAD) to generate NAD-capped RNAs. The biology of mammalian NAD-RNAs, including its turnover and physiological roles are not completely understood. Here we identify NUDT12 as a cytosolic decapping enzyme for NAD-RNAs. Structural, biochemical and functional studies reveal how homodimerization modulates specificity of NUDT12 for NAD-RNAs as substrate. NUDT12 is localized within a few discrete cytoplasmic granules that are distinct from P-bodies. We identity Bleomycin hydrolase (BLMH) as a factor that associates with NUDT12 in a large ~600 kDa dodecamer complex, and we demonstrate that BLMH is required for correct localization of NUDT12 into these granules. This complex is functional in human cell cultures, as artificial tethering of BLMH to a reporter mRNA results in downregulation of reporter expression, similar to that seen with tethering of NUDT12. Analysis of mouse liver transcriptome from the Nudt12 knockout mouse reveals that a select set of RNAs are regulated, including a significant upregulation of circadian clock transcripts. Given that NAD biosynthesis is under circadian control, our study points to a physiological role for the cytosolic surveillance of NAD-RNAs. Overall design: RNA sequencing was used to identify transcript abundance differences between Nudt12-/- and Nudt12+/+  in mouse liver and kidney.   To characterize the effect of NUDT12 absence on circadian gene expression, the RNA sequencing was used to compare gene expression in relation to dark-light cycle.