Replication origins of single-stranded-DNA plasmid pUB110

Abstract

The two replication origins of plasmid pUB110 have been characterized. The site of initiation of DNA replication at the plus origin was mapped to within an 8-base-pair sequence. DNA synthesis initiated at the origin was made to terminate precociously in an inserted sequence of 18 base pairs that is homologous to a sequence in the origin. This suggests that pUB110 replicates as a rolling circle. The minus origin of plasmid pUB10 has been characterized, and the minimal sequence required for function has been determined. As with other minus origins, activity is orientation specific with respect to the direction of replication. Its activity is sensitive to rifampin in vivo, suggesting that RNA polymnerase catalyzes single-strand to double-strand conversion. Unlike all other plasmids of gram-positive bacteria thus far described, the pUB110 minus origin is functional in more than one host.

A fourth class of theta-replicating plasmids: the pAM beta 1 family from gram-positive bacteria.

“…2) did not transform these mutants to erythromycin resistance, while it transformed efficiently the two isogenic Pol+ strains (Table 1). In a control experiment a Pollindependent plasmid, based on the rolling circle pC194 replicon (pHV1610) (38,39) ref. 4).…”

Plasmid Rolling-Circle Replication

“…The ssoU is the most promiscuous sso origin characterized so far, as it seems to be fully functional in many, if not all, Firmicutes (121,(139)(140)(141)(142). The ssoU origin was first identified in staphylococcal plasmid pUB110 (142), within a ∼250-bp DNA fragment with the potential to form several hairpin structures containing symmetric and asymmetric internal loops in addition to the terminal one (139).…”

Lagging-strand origins of the promiscuous plasmid pMV158: physical and functional characterization

“…The mechanisms involved in ss + dsDNA conversion are not well understood, although some features of the process have been defined. First, it seems that only host proteins are involved in the lagging-strand synthesis, most likely RNA polymerase, as shown in vivo for the ssoU of PUB110 (Boe et al, 1989), and in vitro for the ssoA of pT181 (Birch & Khan, 1992). However, in the case of the lactococcal plasmid pWVOl (an ssoAcontaining plasmid) this conversion has been proposed to be mediated by the host DNA primase (Leenhouts e t al., 1991).…”

“…RCreplicating plasmids are constructed like cassettes of genetic information (Projan & Novick, 1988), one of the modules being sso (del Solar e t al., 1993a). Based on sequence homologies, various types of sso have been described (Novick, 1989), including ssoA, which is present in plasmids pT181, pLSl and pC194 (Novick, 1989), and $sou, which is characteristic of plasmid PUB110 (Boe et a/., 1989;Birch & Khan, 1992). A more complex situation is found in the streptococcal plasmid pMV158 (from which plasmid pLSl is derived; Lacks e t al., 1986;Priebe & Lacks, 1989), because it bears both types of sso (van der Lelie e t al., 1989).…”