Control of histone gene expression in Physarum polycephalum. I. Protein synthesis during the cell cycle

Schofield, P.N.; Walker, I.O.

Journal of Cell Science 57: 139-150


ISSN/ISBN: 0021-9533
PMID: 7153256
Accession: 005050087

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Synchronous cultures of P. polycephalum were pulsed with [3H]lysine hydrochloride in S and G2 phases of the cell cycle. Plasmodial extracts were separated into nuclear, ribosomal and acid-soluble postribosomal cytoplasmic fractions. Core histones could be detected by staining in the nuclear fractions of both S and G2 phases but were not detected by staining in the cytoplasmic fractions. Newly synthesized histone was present in S-phase nuclei, but not in S-phase cytoplasm. The specific activity of newly synthesized histone in G2-phase nuclei decreased by at least 95% compared to S phase, and no newly synthesized histone was observed in G2-phase cytoplasmic fractions. Thus, histone synthesis is restricted to S phase. There are no free pools of histone in the cytoplasm of Physarum in either S or G2 phases of the cell cycle.