Structure analysis of two Toxoplasma gondii and Neospora caninum satellite DNA families and evolution of their common monomeric sequence.

CLEMENTE, M.; DE-MIGUEL, N.; LIA, V.; MATRAJT, M; SERGIO OSCAR ANGEL

JOURNAL OF MOLECULAR EVOLUTION

SPRINGER

Año: 2004 vol. 58 p. 557 - 567

0022-2844

A family of repetitive DNA elements of approximately 350 bp—Sat350—that are members of Toxoplasma gondii satellite DNA was further analyzed. Sequence analysis identi.ed at least three distinct repeat types within this family, called types A, B, and C. B repeats were divided into the subtypes B1 and B2. A search for internal repetitions within this family permitted the identi.cation of conserved regions and the design of PCR primers that amplify almost all these repetitive elements. These primers ampli.ed the expected 350-bp repeats and a novel 680-bp repetitive element (Sat680) related to this family. Two additional tandemly repeated high-order structures corresponding to this satellite DNA family were found by searching the Toxoplasma genome database with these sequences. These studies were con.rmed by sequence analysis and identi.ed: (1) an arrangement of AB1CB2 350-bp repeats and (2) an arrangement of two 350-bp-like repeats, resulting in a  680-bp monomer. Sequence comparison and phylogenetic analysis indicated that both high-order structures may have originated from the same ancestral 350-bp repeat. PCR amplification, sequence analysis and Southern blot showed that similar highorder  structures were also found in the Toxoplasmasister  taxon Neospora caninum. The Toxoplasma genome database (http://ToxoDB.org) permitted the assembly of a contig harboring Sat350 elements at  one end and a long nonrepetitive DNA sequence . Flanking this satellite DNA. The region bordering the  Sat350 repeats contained two differentially expressed sequence-related regions and interstitial telomeric sequences.