Repetitive Elements in Genomes of Parasitic Protozoa

Abstract

Repetitive DNA elements have been a part of the genomic fauna of eukaryotes perhaps since their very beginnings. Millions of years of coevolution have given repeats central roles in chromosome maintenance and genetic modulation. Here we review the genomes of parasitic protozoa in the context of the current understanding of repetitive elements. Particular reference is made to repeats in five medically important species with ongoing or completed genome sequencing projects: Plasmodium falciparum, Leishmania major, Trypanosoma brucei, Trypanosoma cruzi, and Giardia lamblia. These organisms are used to illustrate five thematic classes of repeats with different structures and genomic locations. We discuss how these repeat classes may interact with parasitic life-style and also how they can be used as experimental tools. The story which emerges is one of opportunism and upheaval which have been employed to add genetic diversity and genomic flexibility

A variant histone H3 is enriched at telomeres in Trypanosoma brucei

“…The simplest interpretation of our combined localization and ChIP data is that H3V-containing chromatin is enriched at or near telomeres of most, if not all, chromosome ends. We note that the telomeric DNA repeat unit, but not the subtelomeric sequences, are identical in T. brucei, T. cruzi and L. major (Wickstead et al, 2003). It will be interesting to test whether the variant forms of histone H3 that we identified by mining the T. cruzi and L. major sequence databases are also enriched at telomeres.…”

Origins of Microsatellite Diversity in the Trichophyton rubrum - T. violaceum Clade (Dermatophytes)

“…Repetitive sequences were captured with biotinylated (CA) 15 probes and immobilized on avidin-coated beads. The captured DNA was subjected to washing steps and then eluted, amplified, and cloned to produce a library enriched for the target sequence.…”

The L1Tc C-Terminal Domain from Trypanosoma cruzi Non-Long Terminal Repeat Retrotransposon Codes for a Protein That Bears Two C2H2 Zinc Finger Motifs and Is Endowed with Nucleic Acid Chaperone Activity

“…There are about 1,000 copies of the non-LTR retrotransposon L1Tc per T. cruzi haploid genome (4), which has been suggested to confer a significant genomic polymorphism and a high degree of plasticity to the parasite (11,39). L1Tc is actively transcribed in the three stages of the parasite life cycle (21) and codes for the enzymatic machinery involved in its retrotransposition including AP endonuclease, 3Ј phosphatase, 3Ј phosphodiesterase (28,31), reverse transcriptase (RT) (13), and RNase H (29) activities.…”