The effect of sodium n-butyrate on chemical induction of xenotropic virus from synchronized Kirsten sarcoma virus-transformed BALB mouse cells was examined. When added during the last part of the G1 phase, n-butyrate produced a large increase in cycloheximide induction during S phase. Under similar conditions, activation by 5-iododeoxyuridine was inhibited. When added with cycloheximide during the S phase, n-butyrate inhibited activation of virus. Studies with synchronized cultures showed that n-butyrate delayed the onset of DNA synthesis, characteristic of the S phase, and inhibited histone deacetylation in log-phase cells. The effects produced by n-butyrate could, therefore, be the result of lengthening the G1 phase of the cell cycle or a modification of histones affecting transcription during virus activation.

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This work was supported by Contract NO-1-CO-75380 with the National Cancer Institute, NIH, Bethesda, Md. 20205.

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