Identification of a subdomain within DNA-(cytosine-C5)-methyltransferases responsible for the recognition of the 5′ part of their DNA target

Abstract

In previous work on DNA-(cytosine-C5)-methyltransferases (C5-MTases), domains had been identified which are responsible for the sequence specificity of the different enzymes (target-recognizing domains, TRDs). Here we have analyzed the DNA methylation patterns of two C5-MTases containing reciprocal chimeric TRDs, consisting of the N- and C-terminal parts derived from two different parental TRDs specifying the recognition of 5′-CC(A/T)GG-3′ and 5′-GCNGC-3′. Sequences recognized by these engineered MTases were non-symmetrical and degenerate, but contained at their 5′ part a consensus sequence which was very similar to the 5′ part of the target recognized by the parental TRD which contributed the N-terminal moiety of the chimeric TRD. The results are discussed in connection with the present understanding of the mechanism of DNA target recognition by C5-MTases. They demonstrate the possibility of designing C5-MTases with novel DNA methylation specificities.