TSH-treatment of thyroid slices increases the amount of DNA released from nuclei by mild DNase-I digestion

Mechanism of enhanced RNA synthesis in acute-phase rat liver and its relationship to chromatin structure

Nuclei isolated from the liver of rats undergoing an acute inflammatory reaction induced by turpentine treatment show increased RNA synthesis. This increase is essentially determined by a faster polyribonucleotide-elongation rate while the number of transcribing polymerase molecules is unchanged. The sensitivity of chromatin to micrococcal-nuclease digestion and the composition of chromosomal proteins are not affected by the acute-phase process. Therefore the increased RNA synthesis by liver nuclei from acutely inflamed rats does not seem to correlate with major changes in chromatin structure.

Effects of thyrotropin on thyroid chromatin. Enhanced sensitivity to micrococcal nuclease and increased nuclear protein phosphorylation

Thyroid slices were incubated with or without TSH for 2 or 5 h. Nuclei were then prepared, subjected to mild digestion with micrococcal nuclease, and centrifuged at 1200 X g. The amount of DNA in 1200 X g supernatants was increased by TSH at 5 h, but not at 2 h. In parallel studies, thyroid slices were incubated with 32Pi and labeling of acid-soluble nuclear proteins was examined. TSH-dependent increases in labeling of histones H1 and H3, and of the high mobility group protein HMG 14, were observed at 2 h; however, there were no apparent changes in TSH-dependent labeling between 2 and 5 h, in nuclease-sensitive or in bulk chromatin. These results suggest that the observed TSH-dependent changes in the micrococcal nuclease-sensitivity of thyroid nuclear chromatin were not induced directly by changes in the phosphorylation of the histones or HMG 14.