Unusual ribosomal RNA of the intestinal parasite Giardia lamblia.

AUTOR(ES)

Edlind, T D

RESUMO

The anaerobic protozoan Giardia lamblia is a common intestinal parasite in humans, but is poorly defined at molecular and phylogenetic levels. We report here a structural characterization of the ribosomal RNA (rRNA) and rRNA genes of G. lamblia. Gel electrophoresis under native or non-denaturing conditions identified two high molecular weight rRNA species corresponding to the 16-18S and 23-28S rRNAs. Surprisingly, both species (1300 and 2300 nucleotides long, respectively) were considerably shorter than their counterparts from other protozoa (typically 1800 and 3400 nucleotides), and from bacteria as well (typically 1540 and 2900 nucleotides long). Denaturing polyacrylamide gel electrophoresis identified a major low molecular RNA of 127 nucleotides and several minor species, but no molecules with the typical lengths of 5.8S (160 nucleotides) and 5S (120 nucleotides) rRNA. The G. lamblia 1300, 2300, and 127 nucleotide RNAs are encoded within a 5.6 kilobase pair tandemly repeated DNA, as shown by Southern blot analysis and DNA cloning. Thus, the rRNA operon of this eukaryotic organism can be no longer than a typical bacterial operon. Sequence analysis identified the 127 nucleotide RNA as homologous to 5.8S RNA, but comparisons to archaebacterial rRNA suggest that Giardia derived from an early branch in eukaryotic evolution.

Documentos Relacionados

• Cholesterol starvation induces differentiation of the intestinal parasite Giardia lamblia.
• An unusually compact ribosomal DNA repeat in the protozoan Giardia lamblia.
• A single-stranded RNA copy of the Giardia lamblia virus double-stranded RNA genome is present in the infected Giardia lamblia.
• Frequent rearrangements of rRNA-encoding chromosomes in Giardia lamblia.
• Lectin binding by Giardia lamblia.