Sequence of the site-specific recombinase gene cin and of its substrates serving in the inversion of the C segment of bacteriophage P1.

Abstract

Inversion of the 4.2‐kb C segment flanked by 0.6‐kb inverted repeats on the bacteriophage P1 genome is mediated by the P1‐encoded site‐specific cin recombinase. The cin gene lies adjacent to the C segment and the C inversion cross‐over sites cixL and cixR are at the external ends of the inverted repeats. We have sequenced the DNA containing the cin gene and these cix sites. The cin structural gene consists of 561 nucleotides and terminates at the inverted repeat end where the cixL site is located. Only two nucleotides in the cixL region differ from those in the cixR and they are within the cin TAA stop codon. The cin promoter was localized by transposon mutagenesis within a 0.1‐kb segment, which contains probable promoter sequences overlapping with a ‘pseudo‐cix’ sequence cixPp. In a particular mutant, integration of an IS1‐flanked transposon into the cin control region promoted weak expression of the cin gene. The cin and cix sequences show homology with corresponding, functionally related sequences for H inversion in Salmonella and with cross‐over sites for G inversion in phage Mu. Based on a comparison of the DNA sequences and of the gene organizations, a possible evolutionary relationship between these three inversion systems and the possible significance of the cixPp sequence in the cin promoter are discussed.

Multiple inverted DNA repeats of Bacteroides fragilis that control polysaccharide antigenic variation are similar to the hin region inverted repeats of Salmonella typhimurium

“…In S. typhimurium, the reversible expression of two antigenically different flagella, H1 and H2 (Lederberg & Iino, 1956) is controlled by inversion of the hin region which carries a promoter and is upstream of the H2 gene, and a repressor for H1. In Mu and P1 phage DNA inversion alters the tail fibres, thereby changing the phage host range (Plasterk et al, 1983;Hiestand-Nauer & Iida, 1983). There is also some similarity with the Moraxella bovis invertible region which is within the Q/I (formerly b and a) pilus gene (Fulks et al, 1990), the inversion of which mediates pilus phase and antigenic variation.…”

Rates of flagellar- and P1 infective-phase variation by three site-specific recombinase genes in every possible combination.

“…Similarly, for the H segment Cmn and Hin compete in binding to the targets, but Cmn and Pin do not. The gene products predicted from nucleotide sequences of hint, pint, and cin+ consist of 190, 184, and 186 amino acids, respectively (Zieg and Simon 1980;Plasterk et al 1983;Hiestand-Nauer and Iida 1983) and show a considerable degree of homology (Plasterk et al 1983;Hiestand-Nauer and Iida 1983;Kamp et al 1984). N-terminal regions are identical in Pin and Cm, but C-terminal regions are different among the three products.…”

“…Minor differences are also present between the two consensus sequences of IR in the C segment (Hiestand-Nauer and Iida 1983;Jida et al 1984).…”

“…Phage P1 has an invertible C segment, and a cin+ gene adjacent to the segment mediates its inversion (Iida et al 1982;Hiestand-Nauer and Iida 1983). Like a G segment of phage Mu (Kamp et al 1978;Howe et al 1979;van de Putte et al 1980;Grundy and Howe 1984), the C segment has been thought to contain sets of genes for tail fiber polypeptides in the internal region flanked by IRs (Walker and Walker 1983;Iida 1984;Huber et at.…”

“…The three site-specific recombinase genes, hint, piny, and cin+, are functionally related, since they can substitute for one another with respect to inversion of the H and the C segment (Kutsukake and Iino 1980;Enomoto et a1.1983;Tominaga et a1.1986). Structural relationship among the recombinases and between the recombination sites of both segments has been revealed from nucleotide sequences (Zieg and Simon 1980;Hiestand-Nauer and Iida 1983;Plasterk et a1.1983). A recombination mechanism has been studied with the in vitro experimental system using a purified recombinase and its substrate (Johnson and Simon 1985;Huber et at.…”