Vitamin A status affects chromatin structure.

We have examined RNA synthesis by nuclei isolated from testes of rats of varying vitamin A status. Nuclei from retinol-deficient animals showed substantially decreased RNA synthesis by polymerase II when compared to nuclei from normal animals. Within 4 hours after oral administration of retinyl acetate (as the source of retinol) to deficient animals, RNA synthesis by polymerase II had significantly increased. Administration of retinoic acid had a similar but lesser effect. Nucleoside analysis after alkaline hydrolysis of the RNA synthesized by the endogenous polymerase II suggested that the increased activity was due to a greater number of actively transcribing polymerase II molecules on the DNA. Further, when the template capacity of testicular chromatin isolated from deficient and retinyl acetate refed animals was compared, the number of sites recognized by E. coli RNA polymerase was increased twofold after retinyl acetate administration. We conclude that these retinol-induced changes in transcription are due at least in part to changes in chromatin structure.