HIGH-TEMPERATURE INDUCIBLE CELL-FREE TRANSCRIPTION AND REPLICATION OFDOUBLE-STRANDED RNAS WITHIN THE PARASITIC PROTOZOAN CRYPTOSPORIDIUM-PARVUM

Sporozoites of the protozoan parasite, Cryptosporidium parvum, were fo und to contain free, full-size plus strands transcribed from two extra chromosomal, cytoplasmic, virus-like double-stranded RNAs (dsRNAs). Ce ll-free transcription and replication of both dsRNAs were observed in crude sporozoite lysates. RNA polymerase activity was found to be depe ndent upon addition of Mg2+ or Mn2+, as well as the four ribonucleosid e triphosphates, and was insensitive to inhibitors of cellular DNA-dep endent RNA polymerase. Semiconservative transcription of the dsRNAs (p lus strand synthesis) was observed at a wide range of temperatures, wi th an optimum of 50 degrees C. In contrast, replication (minus strand synthesis) was detected only at 50 and 60 degrees C. (C) 1998 Academic Press.