A novel factor for DNA-dependent RNA polymerase II in rat liver nuclei

An increase of the regulating factor for chromatin-dependent RNA polymerase II reactions in the tightly-bound chromatin fraction by glucocorticoid injection

A sugar-containing factor for chromatin-dependent RNA polymerase II reactions exists in rat liver nuclei (1). In this communication the localization of this factor in cell nuclei was investigated. The major activity of the factor was observed in the nuclear soluble fraction whereas a minor activity was detected in the tightly-bound chromatin fraction, but not in the loosely bound chromatin fraction. The factor in the tightly-bound chromatin fraction was considerably increased by glucocorticoid injection, but not in other fractions.

A large-molecular-weight regulating factor for chromatin-dependent RNA polymerase II reactions in rat liver cytoplasm

The author found a sugar-containing 70 KDa factor in rat liver nuclei as described in the previous report (1), which repressed RNA chain initiation by all classes of rat liver RNA polymerases and specifically stimulated chromatin-dependent RNA chain elongation catalyzed by RNA polymerase II. In this communication, the localization of this factor in rat hepatic cells was studied. In the cytoplasmic fraction, a large-molecular-weight regulating activity for chromatin-dependent RNA polymerase II reactions was observed and it was characterized to be a 250 KDa glycoprotein. This factor showed the same biological activity for chromatin-dependent RNA polymerase II reactions as that of the factor reported previously (1). Furthermore, this factor was converted to the 70 KDa factor by the action of exogenous or unknown endogenous protease(s). These results suggest that a conversion mechanism from cytoplasmic factor to nuclear factor for RNA polymerase II-dependent transcription exists.

Modulation of early mRNA synthesis in lectin-induced lymphocyte activation--an association with a possible factor

Two phases of early mRNA synthesis were observed in lectin-induced lymphocyte activation. At 0-2 h, lectin-treated lymphocytes showed a considerable decrease in nuclear RNA polymerase II activity as compared with that of untreated cells and, at later periods, a reverse increase was observed. Such modulation of mRNA synthesis is not due to the change of RNA polymerase II, but a possible factor in nuclei. This factor represses RNA chain initiation and stimulates chromatin-dependent RNA elongation catalyzed by RNA polymerase II. It was characterized to be a 10-30 kDa sugar-containing molecule and the physiological significance of this factor is discussed from the viewpoint of the transcriptional regulation.