No abstract

Class III RNA polymerases purified from the murine plasmacytoma MOPC 315 and from Xenopus Laevis ovaries were compared. The subunit structures of the chromatographically distinct murine enzymes IIIA and IIIa were indistinguishable and were reniarkably similar to that of the amphibian enzyme III. The plasmacytoma class III RNA polymerases were also compared with purified plasmacytoma RNA polymerases I and II. Sedimentation studies indicated that RNA polymerase III is sigriificantly larger than RNA polymerase II, which is slightly larger than RNA polymerase I. Structural analyses showed that the molecular weights of the large subunits present in the clays III enzymes (138,000 and 155,000) differ from those of the class .II enzymes (140,000 and either 170,000, 205,000, or 240,000) and from those of the class I enzymes (117;000 and 195,000). Some low-molecular-weight subunits are also unique to each enzyme class. These results clearly distinguish the class I, II, and I1 enzymes on a structural basis. In addition, polypeptides of molecular weight 29,000 and 19,000 were found in all enzyme classes, a polypeptide of molecular weight 52,000 was found only in class I and III enzymes; and a polypeptide of molecular weight 41,000 was found only in class II and III enzymes. These findings are discussed in terms of the function and regulation of the RNA polymerases.Three majot classes of DNA-dependent RNA polymerases (designated I, II, and III) have been distinguished in lower and higher eukaryotes on the basis of differences in chromatographic and catalytic properties (2-12) and differences in function (1, 10). Class I, II, and III RNA polymerases synthesize, respectively, rRNA, heterogeneous nuclear RNA (HnRNA), and the tRNA and 5S RNA species. In adenovirus-2-infected cells, RNA polymerases II and III have also been shown to synthesize, respectively, viral mRNA precursors and viral 5.5S RNA (11). Whether the individual enzyme forms within each class (5-8, 12-16, 19) (8) and from X. laevis ovaries (7) and, in addition, the subunit structures of the homologous class I, II, and III enzymes from plasmacytoma cells. These studies provide a structural basis for further investigation and understanding of the involvement of the different RNA polymerases in the regulation of specific gene transcription in eukaryotic cells. METHODSRNA polymerases I and II from the murine plasmacytoma MOPC 315 were purified, respectively, through the second phosphocellulose step (13) and through the DEAE-Sephadex step (14). Murine plasmacytoma RNA polymerases IIIA and 11s were solubilized and separated on DEAE-Sephadex as described (8). Enzymes IIIA and IIIB were subsequently purified by chromatography on DEAE-cellulose, CM-Sephadex, and phosphocellulose and by sucrose density gradient sedimentation. All procedures were similar to those described for the purification of RNA polymerases I and II (13,14) and will be described in detail elsewhere (V. E. F. Sklar and R. G. Roeder, manuscript in preparation). Xenopus laevis RNA polymerase III ...

No abstract

No abstract

An outbreak of acute hemorrhagic conjunctivitis (AHC) due to enterovirus type 70 occurred in Dade County, Florida, from September to December 1981. Younger age groups, members of larger households, and the poor were at significantly greater risk of acquiring AHC than others in the community. Schoolchildren were most likely to introduce AHC into the household. After exclusion of all affected children from school, there was a dramatic reduction in reported cases, with attack ratesups, members of larger households, and the poor were at significantly greater risk of acquiring AHC than others in the community. Schoolchildren were most likely to introduce AHC into the household. After exclusion of all affected children from school, there was a dramatic reduction in reported cases, with attack ratesups, members of larger households, and the poor were at significantly greater risk of acquiring AHC than others in the community. Schoolchildren were most likely to introduce AHC into the household. After exclusion of all affected children from school, there was a dramatic reduction in reported cases, with attack rates declining more rapidly for school-aged children than for other age groups. Although AHC spread readily among family members, a retrospective study of 124 affected households showed an association between lower attack rates and simple hygienic measures. Should outbreaks of AHC recur, measures to reduce transmission should include exclusion of affected schoolchildren and educating the public about hygienic precautions.