High mobility group chromosomal proteins isolated from muclei and cytosol of cultured hepatoma cells are similar.

Using sequential chromatography on columns containing immobilized double-stranded DNA and single-stranded DNA, we have purified a protein from the cytosol of an established line of cultured rat hepatoma cells that, by several criteria, is a high mobility group (HMG) protein. Analyses of DNA binding properties, electrophoretic mobilities, amino acid compositions, and immunochemical reactivities reveal that the cytosolic protein is the same protein as HMG-1 isolated from the purified chromatin of the same cell line. Thus, authentic HMG-1 appears to be at least partially responsible for the cytoplasmic fluorescence observed when mammalian cells are stained with fluorescece observed when mammalian cells are stained with fluorescent-labeled, affinity-purified antibodies against HMG-1 [Bustin, M., & Neihart, N.K. (1979) Cell 16, 181-189]. We suggest that HMG-1 cn shuttle between nucleus and cytoplasm, perhaps in response to the nucleus' need for helix destabilizing proteins.