Article

Developmental gene regulation in Giardia lamblia: first evidence for an encystation-specific promoter and differential 5' mRNA processing.

Division of Infectious Diseases, Department of Pathology, University of California at San Diego, 214 Dickinson St., San Diego, CA 92103-8416, USA.
Molecular Microbiology (Impact Factor: 5.03). 10/1999; 34(2):327-40. DOI: 10.1046/j.1365-2958.1999.01602.x
Source: PubMed

ABSTRACT Giardia lamblia must encyst to survive in the environment and subsequently infect new hosts. We investigated the expression of glucosamine-6-phosphate isomerase (Gln6PI), the first enzyme required for biosynthesis of N-acetylgalactosamine, for the major cyst wall polysaccharide. We isolated two Gln6PI genes that encode proteins with large areas of identity, but distinctive central and terminal regions. Both recombinant enzymes have comparable kinetics. Interestingly, these genes have distinct patterns of expression. Gln6PI-A has a conventional, short 5' untranslated region (UTR), and is expressed at a low level during vegetative growth and encystation. The Gln6PI-B gene has two transcripts - one is expressed constitutively and the second species is highly upregulated during encystation. The non-regulated Gln6PI-B transcript has the longest 5'-UTR known for Giardia and is 5' capped or blocked. In contrast, the Gln6PI-B upregulated transcript has a short, non-capped 5'-UTR. A small promoter region (< 56 bp upstream from the start codon) is sufficient for the regulated expression of Gln6PI-B. Gln6PI-B also has an antisense overlapping transcript that is expressed constitutively. A shorter antisense transcript is detected during encystation. This is the first report of a developmentally regulated promoter in Giardia, as well as evidence for a potential role of 5' RNA processing and antisense RNA in differential gene regulation.

0 Bookmarks
 · 
52 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Most eukaryotic mRNAs have 7-methylguanosine caps added to their 5' ends and polyadenylate tails added to their 3' ends, during RNA processing. It has been suggested that the mRNAs of the eukaryote, Giardia lamblia, however, do not possess 5' 7- methylguanosine caps. Giardia's method of translation is particularly of interest be- cause it is believed that Giardia is one of the eukaryote lineages that first branched off from the main line of eukaryotic evolution. I hypothesized that capped mRNA with a poly-A tail would be translated most efficiently in Giardia. In this investigation, four different mRNA constructs containing the luciferase gene were synthesized in vitro and transfected into Giardia lamblia. These mRNA constructs consisted of 5' 7- methylguanosine caps on its mRNA to recruit the ribosome and initiate translation.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In the encystment process of the ciliate protist Colpoda cucullus, we observed that the cell total protein abundance was reduced at 12 h - 1 d after the onset of encystment induction subsequent to the reduction of mRNA abundance. We analyzed the alteration of the expression levels of water-insoluble proteins by two-dimensional polyacrylamide gel electrophoresis using polyoxyethylene (20) sorbitan monooleate (Tween-80), and we identified proteins whose expression levels were altered in the encystment process by a liquid chromatography tandem mass spectrometry analysis. The expression level of a 60-kDa protein (p60; heat shock protein 60) was temporarily enhanced and that of a 55-kDa protein (p55; actin) and a 49-kDa protein (p49; actin) was enhanced in the Colpoda encystment process. In mature cysts, the expression level of p55 and p49 tended to be reduced, whereas the expression level of a 50-kDa protein (p50d; α-tubulin), a 25-kDa protein (p25; α-tubulin) and a 52-kDa protein (p52c; β-tubulin) were enhanced. This article is protected by copyright. All rights reserved.
    Journal of Eukaryotic Microbiology 10/2013; · 2.16 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Giardia lamblia is a protozoan parasite that is found worldwide and has both medical and veterinary importance. We applied the transcription start sequence (TSS-seq) and RNA sequence (RNA-seq) techniques to study the transcriptome of the assemblage A WB strain trophozoite. We identified 8000 transcription regions (TR) with significant transcription. Of these regions, 1881 TRs were more than 500 nucleotides upstream of an annotated ORF. Combining both techniques helped us to identify 24 ORFs that should be re-annotated and 60 new ORFs. From the 8000 TRs, we were able to identify an AT-rich consensus that includes the transcription initiation site. It is possible that transcription that was previously thought to be bidirectional is actually unidirectional.
    PLoS ONE 01/2013; 8(10):e76184. · 3.53 Impact Factor

Full-text (2 Sources)

Download
3 Downloads
Available from
Oct 13, 2014