Nucleolar protein 3 is encoded by NOL3 gene. Multiple transcript variants encoding different isoforms have been found for this gene. So far, Nucleolar protein 3 has show to have two Isoforms. Isoform 1 may be involved in RNA splicing. Isoform 2 functions as an apoptosis repressor that blocks multiple modes of cell death. It inhibits extrinsic apoptotic pathways through two different ways. Firstly, it by interacting with FAS and FADD upon FAS activation blocking death-inducing signaling complex (DISC) assembly. Secondly by interacting with CASP8 in a mitochondria localization- and phosphorylation-dependent manner, limiting the amount of soluble CASP8 available for DISC-mediated activation. It has been shown to down-regulate the enzyme activities of caspase 2, caspase 8 and tumor protein p53.