Project Details


The insect parasite Crithidia fasciculata is a member of the
family Trypanosomatidadae, and shares many unique features with
the related pathogenic genera Trypanosoma and Leishamania.
Though it is not known where transcription initiates for any
protein coding gene in these protozoan parasites, it has been
demonstrated that the 5' termini of probably all mRNAs in these
organisms contain and identical 35 nucleotide untranslated leader
sequence (mini-exon). The sequence is found in a discrete family
of tandem repeat genes which are unlinked to any protein coding
gene. This has led to the suggestion that RNA synthesis in
trypanosomatids is accomplished by the ligation of two unlinked
precursor RNA molecules, a process termed discontinuous

The long term experimental objectives of this research proposal
are to define a transcription unit in C. fasciculata and relate it to
the process of discontinuous transcription. In light of the
uniqueness of this phenomenon, this work may lead to rational
targets for chemotherapy.

The specific experimental proposals are to 1) characterize the
mini-exon gene repeat and its expression in C. fasciculata using
DNA and RNA filter hybridization and DNA sequencing; 2)
characterize the protein coding alpha and beta tubulin genes and
their expression, through cDNA and genomic library construction,
DNA and RNA filter hybridization, and specific transcription rare
measurements. These projects will establish the existence of
discontinuous transcription in Crithidia, define regions of
transcription initiation, and provide necessary material for
succeeding studies. 3) Develop a method of introducing exogenous
DNA into Crithidia and assay for expression. This transfection
system will be used to define sequences required for transcription
initiation and mini-exon addition. 4) Develop an in vitro
transcription system, using Crithidia extracts and DNA templates,
as an alternate approach to studying specific transcriptional

A program of study in relevant molecular biology and
biochemistry is proposed. The overall goal of this proposal is to
acquire the didactic training and laboratory experience necessary
for the Investigator to become an independent biomedical
Effective start/end date1/1/9012/31/91


  • National Institute of Allergy and Infectious Diseases
  • National Institute of Allergy and Infectious Diseases
  • National Institute of Allergy and Infectious Diseases
  • National Institute of Allergy and Infectious Diseases
  • National Institute of Allergy and Infectious Diseases


  • Genetics
  • Molecular Biology


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