While Hax-1 mitochondrial localization has been confirmed in many reports (35) (36) (37) , this is not obviously consistent with its transcript-binding properties. Several other reports have shown localization of the protein to the endoplasmic reticulum (35, 36, 38) , apical membrane of hepatocytes (39) and nuclear envelope (35) . In order to establish Hax-1 cellular localization in rat cells, we performed organellar fractionation and subsequent fractionation of nuclei, followed by SDS-PAGE and western blot. These experiments confirmed the presence of Hax-1 in mitochondria, but also indicated its localization in the nucleus ( Figure 9A ) with only traces of Hax-1 detectable in the cytoplasm. Subsequent nuclear fractionation performed with two different methods, revealed that Hax-1 is present in the fraction containing nuclear matrix proteins ( Figure 9B and C), while it was not detected in the other fractions containing soluble and chromatin-associated proteins.