THE EFFECT OF CHANGES IN THE RESPIRATORY METABOLISM UPON GENOME ACTIVITY A Correlation between Induced Gene Activity and an Increase in Activity of a Respiratory Enzyme

The in vitro regression of experimentally induced chromosome puffs was investigated in explanted salivary gland chromosomes of Drosophila hydei . It was observed that the regression of the puffs 2-32A, 2-36A, 2-48C, and 4-81 B is accelerated if substrates for the respiratory metabolism are supplied to the cells . A similar effect can be produced by addition of KCN or oligomycin to medium in which intact salivary glands are incubated . The acceleration of puff regression by these substances occurs not only if the puff inducing stimulus is removed but as well under conditions in which the stimulus is maintained . Regression of the puffs 2-32A, 2-36A, and 4-81B is inhibited if cycloheximide is present in the incubation medium . Chloramphenicol has no effect on puff regression . Measurements on nicotinamide adenine dinucleotide-dehydrogenase activity in homogenates of salivary glands revealed an increase in enzyme activity of 41 % . Maximum increase is attained at 30 min after the induced puffs have reached their maximum size . The increase in enzyme activity does not occur if the glands are kept in a medium containing either actinomycin D or cycloheximide . Chloramphenicol does not inhibit the increase in enzyme activity . The possible relationship between puff activity and its control as a result of changes in the respiratory metabolism is discussed .