Three tandemly repeated 5S ribosomal RNA-encoding genes identified, cloned and characterized from Cryptosporidium parvum.

We have characterized the 5S rRNA of Cryptosporidium parvum. The gene (rDNA) encoding this 5S rRNA was identified, mapped, the primary and secondary structures determined, and the copy number estimated. Using a PCR-amplified 5S rDNA as a probe, it was shown that this gene can specifically recognize C. parvum genomic DNA, but not other intestinal and environmental organisms tested. Three repeat units of the 5S rDNA found in genomic C. parvum oocyst DNA are within the 2012-bp EcoRI-HindIII fragment and are identical in coding sequence, but differ in flanking regions. Flanking regions are A+T rich (78-89%). The termination signal for polymerase III consists of five thymidine residues at the 3' end of each of three units.