Open AccessExtensive turnover of telomeric DNA at aPlasmodium bergheichromosomal extremity marked by a rare recombinational event
Author(s) -
Marta Ponzi,
Tomasino Pace,
E. Dore,
Leonardo Picci,
Elisabetta Pizzi,
C. Frontali
Publication year - 1992
Publication title -
nucleic acids research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 9.008
H-Index - 537
eISSN - 1362-4954
pISSN - 0305-1048
DOI - 10.1093/nar/20.17.4491
Subject(s) - biology , subtelomere , telomere , breakpoint , plasmodium berghei , repeated sequence , genetics , recombination , tandem repeat , direct repeat , gene conversion , dna , inverted repeat , genome , chromosomal translocation , gene , base sequence , malaria , immunology
The dynamics of telomere turnover were studied in Plasmodium, whose telomeric structures consist of linear, recognisable sequences of two distinct repeats (TTTAGGG and TTCAGGG). Independent recombinant clones containing a well-defined chromosomal extremity of Plasmodium berghei, both before and after a rare insertion event took place, were obtained from clonal parasite populations and analysed. The insertion, which splits the original telomere and causes a significant reduction in the size of the telomeric structure, is shown to consist of an integer number of subtelomeric repeats typical of P.berghei, flanked on both sides by telomere-derived motifs. Analysis of the telomeric repeat sequence heterogeneity in the otherwise homogeneous populations examined, is compatible with a model in which diversification of a given telomere is driven by the occurrence of breakpoints whose frequency rapidly increases along the telomeric tract when moving in the outward direction. The breakpoints might be due either to terminal deletions followed by random serial addition of the two repeat versions, or to recombination events. The shortening/elongation mechanism is favoured against the recombination hypothesis because of the absence of higher-order patterns in the sequence of telomeric repeats.