CAJ | 학술논문

Objective. To clone complete EcoRII restriction endonuclease gene (ecoRllR) and methyltransferase gene(ecoRllM) in one ector and to analyze the coordinating expression of this whole R-M system.Methods. Unidirectional deletion subclones were constructed with ExolII. ecoRllR/M genes were preliminari-ly located in the cloned fragment according to the enzyme activities of subclones. Exact deletion sites were deter-mined by sequencing, and transcriptional start sites were determined by S1 mapping.Results. The DNA fragment which was cloned into pBluescript SK + contained intact ecoRIlR gene andecoRllM gene, anc two transcriptional start sites of ecoRllR gene were determined. 132bp to 458bp from 3' endof ecoRllR gene ar.e indispensable to enzyme activities and deletion of 202bp from 3' end of ecoRllM gene madeenzyme lose the capability in DNA protection to resist specific cut with EcoRII endonuclease (EcoRII. R). Dele-tion of the coding ar d flanking sequences of one gene did not affect the expression of the other gene, and the recombi-nants only containing ecoRllR gene appeared to be lethal to dcm+ host.Conclusion. scoRllM gene linking closely to ecoRIIR gene is very important for the existence of the R-M sys-tem in process of evolution, but the key to control EcoRlI R-M order may not exist in transcriptional level .``Liu Jmy,Corresponding author.