Effects of X- and Ultra-violet Irradiation on the Incorporation of Phosphorus-32 into Isolated Nuclei of Rabbit Appendix

Abstract

IN previous studies¹ it was observed that the removal of deoxyribonucleic acid from rabbit appendix nuclei isolated in sucrose severely impairs the incorporation of phosphorus-32 into deoxyribonucleic acid, ribonucleic acid, and into organic acid-soluble phosphate. The lost capacity for incorporation can be restored by the addition of some polyanionic compounds, such as calf thymus deoxyribonucleate, yeast ribonucleate, or chondroitin sulphate. By treating the nuclei with pancreatic deoxyribonuclease in the presence of chondroitin sulphate, we have now succeeded in removing the bulk of deoxyribonucleic acid from the nucleus without appreciably affecting its capacity for incorporation (Table 1). An essentially similar but far more extensive observation has recently been reported by Allfrey and Mirsky² on the incorporation of labelled precursors into proteins and ribonucleic acids of calf thymus nuclei. However, the incorporation of phosphorus-32 into deoxyribonucleic acid was rather exceptional in this respect, because it could not be retained by chondroitin sulphate when the removal of deoxyribonucleic acid was too extensive (Table 1). This observation confirms the previous finding using sodium nucleates as the restoring agent¹.