Abstract
The incorporation in vivo of L-[14C]lysine into nuclear and microsomal protein fractions in regenerating liver was studied at various intervals after partial hepatectomy. Incorporation into histone was depressed 1.5-12 hr. and equal and above average 12-22.5 hr. after the operation; incorporation into the hydrochloric acid-insoluble fractions of nuclei and of the perfluoro-octanoate pellet was relatively enhanced to varying extents during the whole period. The results make it probable that the synthesis of histone required for cell division begins before the synthesis of DNA.