Streptomyces linear plasmids that contain a phage‐like, centrally located, replication origin

Abstract

Unlike previously studied linear replicons containing 5' DNA termini covalently bound to protein, pSLA2, a 17 kb linear plasmid of Streptomyces rochei, initiates replication internally rather than at the telomeres (Chang and Cohen, 1994). Here we identify and characterize the replication origin of pSLA2, showing that it contains a series of direct repeats (iterons) within a centrally located gene encoding an essential DNA-binding protein (Rep1); a second essential protein (Rep2), which resembles prokaryotic DNA helicases and has ATPase activity stimulated by single-stranded DNA, is expressed from the same transcript. A 430 bp locus separated by almost 2 kb from the iterons of the origin specifies an as yet undefined additional function required in cis for plasmid replication. pSCL, a 12 kb linear plasmid of Streptomyces clavuligerus, contains, near the centre of the plasmid, a region configured like the pSLA2 origin. The replication regions of pSLA2 and pSCL, which are capable of propagating plasmid DNA in either a circular or linear form (Shiffman and Cohen, 1992; Chang and Cohen, 1994) resemble those of temperate bacteriophages of the Enterobacteriacae and Bacillus. Our observations suggest that Streptomyces linear plasmids may occupy an evolutionarily intermediate position between circular plasmids and linear phage replicons.

Three functional replication origins of the linear and artificially circularized plasmid SCP1 of Streptomyces coelicolor

“…SCP1, SLP2, pSLA2, pSLA2-L, pSCL1, pSCL2, pRL2, pRL4, pFRL2 and pSHK1) commonly contain one internal replication origin (Shiffman & Cohen, 1992;Chang et al, 1996;Redenbach et al, 1999;Huang et al, 2003;Hiratsu et al, 2000;Wu et al, 2006;Xu et al, 2006a;Zhang et al, 2009). Recently, Zhang et al (2010) found that 54 kb pFRL1 contained two replication loci.…”

“…Some Streptomyces linear plasmids can also propagate in circular mode when their telomeres are deleted and the ends are fused (Shiffman & Cohen, 1992;Chang & Cohen, 1994). The centrally located replication locus of pSLA2 consists of a rep gene (encoding a DNA helicase) and its adjacent iteron (Chang et al, 1996). Such rep (helicase/iteron) loci are also found in SCP1, SLP2, pSCL1 and pSHK1 (Shiffman & Cohen, 1992;Wu & Roy, 1993;Redenbach A naac(3)IV gene inserted near rep3A of SCP1 This work A3(2) (SCP1Drep1A) A naac(3)IV gene inserted at rep1A of SCP1 This work A3(2) (SCP1Drep3A) A naac(3)IV gene inserted at rep3A of SCP1 This work A3(2) (SCP1Drep1ADrep3A) An aac(3)IV gene inserted at rep3A and a kan gene at rep1A of SCP1…”

Identification of two linear plasmids in the actinomycete Planobispora rosea

“…The mechanism of replication of the former type of linear replicon has not yet been detailed, whereas two different replication strategies have been described in the latter type: (i) 029 replication starts at both ends, using the terminal protein as the primer, and proceeds throughout the whole DNA molecule ; (ii) several streptomycete plasmids and linear chromosomes, as well as the linear plasmids of Borrelia, appear to replicate bidirectionally from a unique internal origin ; in such instances, telomere-promoted replication appears to be confined to the terminal regions of the On: Sun, 13 May 2018 08:27:29 S. POLO a n d O T H E R S linear molecule (Casjens & Huang, 1993;Chang & Cohen, 1994;Chang et al, 1996). Planobispora rosea is an actinomycete that produces the antibiotic GE2270, a thiazolyl peptide inhibitor of the translation elongation factor Tu (Goodfellow, 1992;Selva et al, 1991;Anborgh & Parmeggiani, 1991;Tavecchia et al, 1995).…”

Characterization of the Streptomyces lavendulae IMRU 3455 linear plasmid pSLV45

“…All these plasmids were found to contain TIRs and TPs. In addition, both pSLA2 and SLP2 were shown to contain an internal origin of replication for bi-directional replication of DNA (Chang & Cohen, 1994;Chang et al, 1996;Huang et al, 2003).…”

“…All these plasmids were found to contain TIRs and TPs. In addition, both pSLA2 and SLP2 were shown to contain an internal origin of replication for bi-directional replication of DNA (Chang & Cohen, 1994;Chang et al, 1996;Huang et al, 2003).Unlike the chromosomes of most bacteria, which are circular in nature, the chromosomes of actinomycetes are linear (Lezhava et al, 1995;Lin et al, 1993). This was first demonstrated in S. lividans and has now been established for several other actinomycetes including S. coelicolor, Streptomyces griseus and Saccharopolyspora erythraea (formerly Streptomyces erythraeus) (Lezhava et al, 1995;Lin et al, 1993;Reeves et al, 1998).…”