Variation in DNA swivel enzyme activity during the mammalian cell cycle

Abstract

Synchronized cells of a normal human lymphocytic cell line contain little swivel enzyme activity in G₀ and G₁ and high activity in S phase. The level of activity in different growth phases appears to be related to the fraction of the population engaged in DNA replication. No endogenous inhibitor or activator of swivel activity could be demonstrated. The evidence implies that the enzyme may be present only during S phase; it is therefore a possible control factor for replication.