Characterisation of a retinoic-acid-binding component from F9 embryonal-carcinoma-cell nuclei

When F9 murine-embryonal-carcinoma cells were incubated with all-trans-[3H]retinoic acid, approximately 10% of the tritium label taken up by the cells was recovered in the nuclei. Sonication or DNase I digestion followed by extraction with 0.6 M NaCl released 20-40% of the nuclear-associated retinoic acid. Analysis of these extracts showed that retinoic acid was bound to protein sedimenting at 4 S. This nuclear retinoic-acid-binding component bound all-trans- and 13-cis-retinoic acid with comparable affinity whereas retinol competed less efficiently for binding. These results suggest that F9 embryonal-carcinoma cells contain a nuclear binding protein for retinoic acid that is distinct from the cellular retinoic-acid-binding protein.