The attC is a site specific recombination hot spot of different mobile elements

QUIROGA C; CENTRÓN D

Mar del Plata, Argentina

Jornada; XLIII Reunio Anual de la Sociedad Argentina de Investigacion en Bioqu¨ªmica y Biolog¨ªa Molecular; 2007

Sociedad Argentina de Investigaci¨®n en Bioqu¨ªmica y Biolog¨ªa Molecular

The attC sites are genetic elements involved in the site-specific recombination of gene cassettes mediated by a tyrosine recombinase integrase, and in the recombination of class C-attC group II (CattG2) introns. Their general structure consists of two short regions of sequence similarity at their boundaries (1R-2R and 1L-2L) separated by a stretch of imperfect internal dyad symmetry. The attC sites form stem-loop structures through a single strand DNA intermediate. The goal of this work was to understand the evolution of three genetic elements: attCs, integrases and CattG2 introns, which converge in two different site-specific recombination mechanisms. Seventy bacterial genomes were selected by their identity to the S.ma.I2 intron, inserted within an attC site of a class 1 integron. Only 11 introns (15.7%) showed an ¡Ý 46 % identity to S.ma.I2 and belonged to a genome that also encoded an integrase. Sequence analysis with computational tools of these target sites showed that all CattG2 introns invade the TTGTT motif and were inserted downstream of or in stem-loops structures. Uninvaded versions of these target sites were found disseminated through other bacterial genomes. Three out of 5 stems were located within chromosomal integrons, which suggest that they can be identified as typical attC sites. Hence, genome evolution seems to converge in the use of a common target site for two different recombination systems.