Mitochondrial protein p32 can accumulate in the nucleus

Human p32 was first isolated associated with the splicing factor ASF/SF-2, The p32 protein is translated as pre-protein from which a mitochondrial imp ort signal is cleaved off to create the mature p32. The majority of p32 is consequently found in the mitochondria. In this study we investigated extra mitochondrial p32. An increased nuclear localisation of endogenous p32 was demonstrated as a response to leptomycin B or actinomycin D treatment of ce lls. Mature p32 gene and deletion mutants were cloned into enhanced green f luorescence protein reporter plasmids. On transfection, EGFP-p32 protein wa s mainly localised to the cytoplasm and to a lesser extent to the nucleus o f transfected COS cells. Upon treatment with actinomycin D or leptomycin B, the EGFP-p32 protein accumulated in the nucleus. Deletion analysis indicat ed which regions of EGFP-p32 are involved in nuclear export and nuclear imp ort. (C) 2001 Academic Press.