RNA synthesis and number of transcribing polymerase molecules in ischemic liver nuclei

Summary Nuclei isolated from ischemic liver show a consistent reduction of their RNA synthesis. The reduction persists at high ionic strength and in the presence of heparin, when RNA synthesis in vitro is fully activated and occurs in the presence as well as in the absence of a-amanitin. Both the number of transcribing polymerase molecules and the rate of elongation of initiated polynucleotide chains seem to be equally affected.     

Effect of estradiol on the RNA content and the activity of nucleolar RNA polymerase from rooster liver

Estradiol administration to roosters results in changes in the macromolecular composition of the liver. Besides a gradual increase in liver protein and a sudden enhancement of liver DNA after 24 hours, the most pronounced change occurs in the RNA content, viz. an increase up to 190% of controls starting 26 hours after estradiol administration.The activity of nucleolar RNA polymerase -solubilized and chromatographed on DEAE-Sephadex- is increased four-fold 26 hours after estradiol treatment. This increase was found to be due to an increased initiation frequency. Concurrently, the initiation characteristics of nucleolar RNA polymerase are changed.     

m6A RNA methylation regulates promoter- proximal pausing of RNA polymerase II

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Dexamethasone increases the number of RNA polymerase II molecules transcribing integrated mouse mammary tumor virus DNA and flanking mouse sequences.

In mouse Ltk- cells that were transfected with recombinant bacteriophage DNA containing a complete proviral copy of an integrated endogenous mouse mammary tumor virus (MMTV) with its flanking cellular sequences, the newly acquired MMTV proviruses were transcribed in a glucocorticoid-responsive fashion. After hormone treatment of selected cell clones in culture we isolated the nuclei, elongated the nascent RNA chains in vitro, and determined the number of RNA polymerase II molecules on the transcribed MMTV DNA as well as on the flanking mouse DNA sequences. We found that the specific increase in the polymerase loading after hormone treatment is proportional to the increase in the amount of stable MMTV mRNA. When the DNA sequences which are responsible for hormone-receptor binding and for the increased MMTV mRNA levels were deleted, no increase in RNA polymerase II loading on MMTV DNA was observed. Nuclear RNA chains which were transcribed in response to hormone treatment were detected not only from the transfected MMTV DNA but also from the mouse DNA sequences adjacent to the 3' end of the provirus.     

RNA polymerase: structural similarities between bacterial RNA polymerase and eukaryotic RNA polymerase II

Bacterial RNA polymerase and eukaryotic RNA polymerase II exhibit striking structural similarities, including similarities in overall structure, relative positions of subunits, relative positions of functional determinants, and structures and folding topologies of subunits. These structural similarities are paralleled by similarities in mechanisms of interaction with DNA.     

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

The author found, in rat liver nuclei, a novel factor which exhibited a strong inhibitory effect on RNA chain initiation by various classes of RNA polymerases (I, II and III) using an exogenous DNA template.The molecular weight of this factor was estimated to be 70 K daltons, and its activity was not affected by treatment with trypsin, RNase A, lipase C, -amylase and heat. However, its activity was inactivated by a digestion of glycosidases. The molecule is shown to contain a considerable amount of sugars by physicochemical analysis. In addition, it is elucidated that the factor is not heparin which has a similar biological activity.     

Tails of RNA polymerase II

Eukaryotic RNA polymerase II contains two distinct structural domains: a catalytic core consisting of subunits that are homologous to other multisubunit RNA polymerases, and a unique extension of the carboxy-terminus of the largest subunit comprising tandem repeats of the seven amino acid sequence YSPTSPS. This repetitive 'tail' domain is essential for polymerase function in vivo. Although the nature of this essential function is unknown, actively transcribing RNA polymerase II is known to be multiphosphorylated on this repetitive domain.     

Initiation of RNA molecules by purified Escherichia coli RNA polymerase

Summary The kinesties of appearance of, and the distribution among, the four bases of the chain-initial nucleotides (5-termini) of RNA chains synthesized in vitro under various conditions have been investigated. The results of this study have shown that when native T4 bacteriophage DNA is the template for the RNA polymerase, most chains start with a purine nucleotide. The ratio of ATP termini to GTP termini is independent of the reaction time and of the template/enzyme ratio in the reaction mixture. A similar preferential purine initiation was observed when denatured T4 is the template, but the ratio of ATP to GTP termini is reduced. All 5-termini of poly-AU chains synthesized on poly-dAT templates are ATP.The determination of the kinetics of initiation of RNA chains has allowed direct confirmation of some conclusions which had been inferred previously from sedimentation analyses of the RNA product. (1) Most RNA chains are initiated during a short period at the outset of the reaction. (2) Low concentrations of native DNA templates limit the number of RNA chains synthesized, not the rate of RNA chain growth. (3) The maximum number of RNA molecules which can be synthesized on denatured DNA templates is severalfold larger than the maximum number which can be synthesized on the same weight of native DNA.     

6S RNA regulates E. coli RNA polymerase activity

The E. coli 6S RNA was discovered more than three decades ago, yet its function has remained elusive. Here, we demonstrate that 6S RNA associates with RNA polymerase in a highly specific and efficient manner. UV crosslinking experiments revealed that 6S RNA directly contacts the sigma70 and beta/beta' subunits of RNA polymerase. 6S RNA accumulates as cells reach the stationary phase of growth and mediates growth phase-specific changes in RNA polymerase. Stable association between sigma70 and core RNA polymerase in extracts is only observed in the presence of 6S RNA. We show 6S RNA represses expression from a sigma70-dependent promoter during stationary phase. Our results suggest that the interaction of 6S RNA with RNA polymerase modulates sigma70-holoenzyme activity.