The intracellular pyrimidine 5′-nucleotidase NT5C3A is a negative epigenetic factor in interferon and cytokine signaling

Abstract

The enzyme pyrimidine 5'-nucleotidase (NT5C3A), which mediates nucleotide catabolism, was previously thought to be restricted to blood cells. We showed that expression of the gene encoding NT5C3A was induced by type I interferons (IFNs) in multiple cell types and that NT5C3A suppressed cytokine production through inhibition of the nuclear factor κB (NF-κB) pathway. <i>NT5C3A</i> expression required both an intronic IFN-stimulated response element and the IFN-stimulated transcription factor IRF1. Overexpression of NT5C3A, but not of its catalytic mutants, suppressed IL-8 production by HEK293 cells. Whereas knockdown of <i>NT5C3A</i> enhanced tumor necrosis factor (TNF)-stimulated IL-8 production, it reduced the IFN-mediated suppression of <i>Il8</i> expression. Overexpression of <i>NT5C3A</i> increased the abundance of NAD⁺ and the activation of the sirtuins SIRT1 and SIRT6, which are NAD⁺-dependent deacetylases. NT5C3A-stimulated sirtuin activity resulted in deacetylation of histone H3 and the NF-κB subunit RelA (also known as p65), both of which were associated with the proximal region of the <i>Il8</i> promoter, thus repressing the transcription of <i>Il8</i> Together, these data identify an anti-inflammatory pathway that depends on the catalytic activity of NT5C3A and functions as a negative feedback regulator of inflammatory cytokine signaling.