Antigen expression from the ribosomal DNA repeat unit of Giardia intestinalis.
The amitochondrial human intestinal parasite Giardia intestinalis is regarded to be the most ancient living example of single-celled eukaryotes and should display primitive features of pre-metazoan gene regulation. Characterization of E. coli clones which express Giardia antigens from plasmid vectors has revealed that an antigen is encoded by the rDNA repeat unit from the strand complementary to that encoding the rRNAs. The open reading frame (ORF) originates in the spacer region between the small (SS) and large (LS) subunit rRNA genes and terminates within the LS rRNA gene. The promoter region of this ORF has characteristics of both RNA polymerase (pol) II and pol III regulatory sequences, suggestive of gene regulation before these different promoter types evolved. The rDNA repeat unit is located on multiple chromosomal sites which are different in each isolate, although the electrophoretic karyotypes appear very stable in Giardia from both human and animal sources.
Upcroft
J A
JA
Queensland Institute of Medical Research, Brisbane, Australia.
Healey
A
A
Mitchell
R
R
Boreham
P F
PF
Upcroft
P
P
D000595:Amino Acid Sequence; D000818:Animals; D000953:Antigens, Protozoan / Q000096:biosynthesis / Q000235:genetics*; D001483:Base Sequence; D004275:DNA, Ribosomal / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation; D005872:Giardia / Q000235:genetics* / Q000276:immunology; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D011401:Promoter Regions, Genetic; D012319:RNA Polymerase II / Q000235:genetics; D012320:RNA Polymerase III / Q000235:genetics; D012045:Regulatory Sequences, Nucleic Acid; D012091:Repetitive Sequences, Nucleic Acid; D015183:Restriction Mapping
D000953:Antigens, Protozoan; D004275:DNA, Ribosomal; D012319:RNA Polymerase II; D012320:RNA Polymerase III