Transcription regulation of restriction-modification system Ecl18kI

Abstract

Restriction-modification (R-M) system Ecl18kI is representative of R-M systems whose coordinated transcription is achieved through a separate DNA-binding domain of the methyltransferase. M.Ecl18kI recognizes an operator sequence located in the noncoding region that separates the divergently transcribed R and M genes. Here we show that, contrary to previous predictions, the two ecl18kI promoters are not divergent, but actually face one another. The binding of M.Ecl18kI to its operator prevents RNA polymerase (RNAP) binding to the M promoter by steric exclusion, but has no direct effect on RNAP interaction with the R promoter. The start point for R transcription is located outside of the intergenic region, opposite the initiation codon of the M gene. Regulated transcription of the potentially toxic ecl18kI R gene is accomplished (i) at the stage of promoter complex formation, through direct competition from complexes formed at the M promoter, and (ii) at the stage of promoter clearance, since R promoter-bound RNAP escapes the promoter more slowly than RNAP bound to the M promoter.

Flexibility of the Linker between the Domains of DNA Methyltransferase SsoII Revealed by Small-Angle X-Ray Scattering: Implications for Transcription Regulation in SsoII Restriction–Modification System

“…M.SsoII can also act as a transcription factor binding to a 15-bp quasipalindromic sequence 5′-AGGACAAATTGTCCT-3′/3′-TCCTGTTTAACAGGA-5′ (the regulatory site) in the intergenic region of the SsoII R–M system and therefore downregulating the expression of its own gene and stimulating the expression of the cognate RE gene [12], [13]. The same mechanism of action is shown for M.Ecl18kI [14], which differs from M.SsoII by a single amino acid residue. Some other C5-DNA MTases are shown experimentally to repress their own genes without any impact on expression of the corresponding REs, namely M.EcoRII [15], [16], M1.LlaJI [17], M.MspI [18], and M.ScrFIA [19].…”

Antisense RNA associated with biological regulation of a restriction–modification system

“…Their regulation was found to be associated with interference between the two convergent promoters (25,50). In these R–M systems, as well as in MspI (59), two feedback loops have been identified.…”

Diverse Domains of (Cytosine-5)-DNA Methyltransferases: Structural and Functional Characterization

“…According to the [66][67][68]. Among them, M.SsoII and M.Ecl18kI are the most remarkable ones as they not only suppress the transcription of their own genes but also stimulate the transcription of their cognate RE genes.…”

“…Moreover, it has been shown recently that M.SsoII binding to the regulatory site prevents its interaction with the methylation site. Thus, the two functions of the protein are mutually exclusive [67,81]. …”