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Virus-like, double-stranded RNAs in the parasitic protozoan Cryptosporidium parvum

N V Khramtsov1, K M Woods, M V Nesterenko

  • 1Division of Biology, Kansas State University, Manhattan 66506, USA. podolsk@ksu.edu

Molecular Microbiology
|February 12, 1998
PubMed

Insights

Novel double-stranded RNAs (dsRNAs) were discovered in Cryptosporidium parvum. These dsRNAs encode proteins similar to viral RNA-dependent RNA polymerases and may be involved in parasite biology.

Area of Science:

  • Parasitology
  • Virology
  • Molecular Biology

Background:

  • Cryptosporidium parvum is a significant protozoan parasite causing gastrointestinal illness.
  • Extrachromosomal genetic elements in parasites are not well understood.

Purpose of the Study:

  • To identify and characterize novel genetic materials within Cryptosporidium parvum.
  • To investigate the potential origin and function of these elements.

Main Methods:

  • Isolation and sequencing of double-stranded RNAs (dsRNAs) from C. parvum oocysts.
  • Bioinformatic analysis of dsRNA sequences and encoded proteins.
  • Detection of RNA-dependent RNA polymerase (RDRP) activity in parasite extracts.

Main Results:

  • Two novel linear extrachromosomal dsRNAs were identified in North American C. parvum isolates.
  • The larger dsRNA (L-dsRNA) encodes a protein with homology to viral RDRPs, particularly fungal polymerases.
  • The smaller dsRNA (S-dsRNA) encodes a protein with limited similarity to mammalian JNK.
  • RDRP activity was detected in C. parvum sporozoite extracts, producing products similar to the purified dsRNAs.
  • dsRNAs were sensitive to RNase A, suggesting they may be unencapsidated.

Conclusions:

  • The discovered dsRNAs represent a novel finding in Cryptosporidium parvum.
  • The presence of RDRP-like sequences suggests a potential viral or self-replicating RNA origin.
  • These dsRNAs may play a role in the biology or pathogenesis of C. parvum.

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