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.