Solubilized DNA‐dependent RNA polymerase from human placenta: A Mn²⁺‐dependent enzyme

Abstract

The 100-fold purified RNA polymerase activity from human placenta is completely dependent upon added DNA. The enzyme is most active at 3 mM Mn 2+ in the presence of 100 mM (NI-I4)2 SO4. Denatured DNA is a better template than native DNA. 0~Amanitin completely inhibits the incorporation of ~H-UMP, while rifampicin has no influence upon the enzymatic activity.

Characterization of RNA polymerase type II from human term placenta

“…The requirements of placental RNA polymerase type I1 activity and preference for denatured template over native DNA, and Mn over Mg correspond with those of calf thymus RNA polymerase type I1 and, for that matter, with all nuclear RNA polymerase type I1 enzymes isolated thus far from mammals (Roeder, 1976). The data reported here confirm and extend the earlier findings by Voigt et al (1970) and Kaufmann and Voigt (1973), who purified this placental enzyme by DEAE-cellulose chromatography.…”

“…The first work on partially purified human placental RNA polymerase type I1 came from the Max-Planck Institute (Mertelsmann and Matthaei, 1968;Mertelsmann, 1969;Voigt et al, 1970;Kaufmann and Voigt, 1973). RNA polymerase type I1 was purified by DEAEcellulose chromatography and characterized with respect to optimal ionic strength, pH, template, and metal requirements, and to its sensitivity to several toxins and steroids in in vitro experiments.…”

Actions of the rifamycins.

“…Studies with RNA polymerase from rat liver nuclei (174) and ascites cells (171) showed that they contained an enzyme insensitive to rifamycins. These results have been confirmed with solubilized RNA polymerase isolated from rat liver, human placenta nuclei, and lymphoid tissue; the activity of these enzymes depended completely on the addition of DNA (43,65,172). Furthermore, both RNA polymerase A and B isolated from calf thymus were not affected by the antibiotic (72).…”

Rifamycins: A General View

“…Rifampicin and rifamycin SV have been tested against crude extracts of DNA-dependent RNA polymerase from rat liver nuclei (145) and from as cites cells (64). Rifampicin has been shown to be inactive when tested on solubilized, DNA-dependent RNA polymerases from rat nuclei (146), from lymphoid tissue (147), and from human placenta (148).…”