Isolation and preservation of cell nuclei for studies on RNA polymerase activity

The suitability of saponin for the isolation and of glycerol for the preservation of mammalian cell nuclei has been investigated. The nonionic detergent saponin was found to be a useful cell lytic agent in a procedure for the isolation of nuclei from several mammalian cell types. The RNA polymerase activity of rat liver nuclei was not affected by treatment with saponin or with some other nonionic detergents that were tested. Low concentrations of ionic agents also did not affect the activity of the enzyme though higher concentrations caused lysis of the nuclei. The preservation of structure and enzyme activity in the isolated nuclei was achieved by storage at low temperature in a medium containing 70% glycerol together with a suitable concentration of a divalent metal and phosphate buffer.

Some effects of testosterone on the rat ventral prostate

1. Labelled testosterone, injected directly into the ventral prostate of castrated rats became associated, in part, with a cytoplasmic high-molecular-weight fraction, fraction ;A'. 2. The label present in fraction ;A' was found to be mainly associated with dihydrotestosterone. 3. Unlike fraction ;A' from testosterone-pelleted castrated rats, fraction ;A' obtained from untreated castrated rats, 48h or more after castration, was strongly inhibitory towards Escherichia coli RNA polymerase in vitro. 4. The inhibition of RNA polymerase by fraction ;A' from castrated rats was not changed by the addition of testosterone or dihydrotestosterone in vitro, but pre-heating it to 80 degrees C resulted in a loss of its inhibitory capacity. 5. Fraction ;A' from castrated rats contained ribonuclease activity. The elution profile of ribonuclease activity from Sephadex columns indicated that this activity was responsible for the inhibitory effect on the RNA polymerase assays. 6. It is concluded that, unlike the inhibitor present in the uterus of ovariectomized rats (Talwar, Segal, Evans & Davidson, 1964), no direct connexion exists between the steroid-binding capacity of prostatic fraction ;A' and its effect on E. coli RNA polymerase activity in vitro.

Micro-analysis of pure deoxyribonucleic acid-dependent ribonucleic acid polymerase from Escherichia coli. Action of heparin and rifampicin on structure and function

By using micro disc electrophoresis and micro-diffusion techniques, the interaction of pure DNA-dependent RNA polymerase (EC 2.7.7.6) from Escherichia coli with the template, the substrates and the inhibitors heparin and rifampicin was investigated. The following findings were obtained: (1) heparin converts the 24S and 18S particles of the polymerase into the 13S form; (2) heparin inhibits RNA synthesis by dissociating the enzyme-template complex; (3) rifampicin does not affect the attachment of heparin to the enzyme; (4) the substrates ATP and UTP are bound by enzyme loaded with rifampicin; (5) rifampicin is bound by an enzyme-template complex to the same extent as by an RNA-synthesizing enzyme-template complex. From this it is concluded that the mechanism of the inhibition of RNA synthesis by rifampicin is radically different from that by heparin. As a working hypothesis to explain the inhibitory mechanism of rifampicin, it is assumed that it becomes very firmly attached to a position close to the synthesizing site and only blocks this when no synthesis is in progress.

Effects of salicylate on RNA polymerase activity and on the incorporation of orotic acid and thymidine into the nucleic acids of rat foetuses in vitro

Salicylate (10 mM) significantly inhibited the activity of RNA polymerase and the incorporation of radioactivity from orotic acid-5-3H and thymidine-6-3H into whole 13 day and 16 day rat foetuses. The polymerase activity and the incorporation of the labelled orotate were significantly inhibited by 2 mM salicylate in the 16 day foetus only. The inhibitory action of salicylate on RNA biosynthesis may be related to its effects in causing an increased incidence of foetal death and congenital malformation in pregnant rodents.