Differences in LexA regulon structure among Proteobacteria through in vivo assisted comparative genomics

Abstract

The LexA regulon encompasses an ensemble of genes involved in preserving cell viability under massive DNA damage and is present in most bacterial phyla. Up to date, however, the scope of this network had only been assessed in the Gamma Proteobacteria. Here, we report the structure of the LexA regulon in the Alpha Proteobacteria, using a combined approach that makes use of in vitro and in vivo techniques to assist and validate the comparative genomics in silico methodology. This leads to the first experimentally validated description of the LexA regulon in the Alpha Proteobacteria, and comparison of regulon core structures in both classes suggests that a least common multiple set of genes (recA, ssb, uvrA and ruvCAB) might be a defining property of the Proteobacteria LexA network.

Identification of the Acidobacterium capsulatum LexA box reveals a lateral acquisition of the Alphaproteobacteria lexA gene

“…First described in R. sphaeroides (Fernández de Henestrosa et al, 1998), the Alphaproteobacteria LexA box is monophyletic for this proteobacterial subclass (Erill et al, 2004), and presents a direct-repeat structure that, up to now, had not been described for any other bacterial clade. This fundamental departure from the standard palindromic structure of all other known LexAbinding motifs, together with a highly divergent protein sequence, have made it difficult to reconstruct the precise evolutionary history of the Alphaproteobacteria LexA, but we have previously shown that its most probable origin lies in an evolutionary pathway different from the one that gave rise to the Gamma-and Betaproteobacteria LexA proteins (Mazó n et al, 2004b).…”

“…Comparative analyses of the SOS system in different subclasses of the Proteobacteria (Alpha, Beta and Gamma) indicate that a common set of genes (lexA, recA, ssb, uvrA and ruvA) is directly repressed by LexA in all these subclasses, and therefore constitutes the canonical gene composition of the SOS regulon in this phylum (Erill et al, 2003(Erill et al, , 2004. Some of these genes (lexA, recA and ruvA) are also regulated by LexA in Bacillus subtilis (Dubnau & Lovett, 2002).…”

A resposta SOS de Caulobacter crescentus e relações dos mecanismos de reparo com a progressão do ciclo celular.

“…Este antibiótico se liga a RNA polimerase bacteriana, impondo um sério bloqueio à transcrição; mutações no gene rpoB, que codifica a subunidade β da RNA polimerase, são capazes de tornar as células resistentes à rifampicina (Garibyan et al, 2003 no momento do experimento, a cultura esteja em fase logarítmica de crescimento, pois é neste período que a proporção de células móveis é maior (Iba et al, 1975 9 (± 193,5) Os dados de expressão relativa, bem como a pontuação e posição da caixa SOS em relação ao códon de início anotado no genoma de C. crescentus estão na tabela 5 abaixo, classificados de acordo com os níveis de expressão. (13)(14)(15)(16)(17)(18)(19)(20) ATGTTCTCG).…”

“…The structure of the regulon can vary depending on the organism, but still, a canonical set of genes has been proposed to be LexA regulated in all Proteobacteria studied to date. It is comprised of lexA, recA, ssb, uvrA, and ruvCAB (19).…”

“…Após a formação do septo de divisão na célula pré-divisional, ocorre a degradação de CtrA em seu compartimento séssil (Judd, 2003), ficando garantida, dessa forma, a inibição da replicação na célula móvel nascente e o contrário na célula talo. 19 Existem hoje poucos trabalhos focando mecanismos de reparo de DNA em C.…”