Primary structure and expression of the Xiphophorus DNA-(cytosine-5)-methyltransferase XDNMT-1

Small aquarium fishes become increasingly important in the study of normal vertebrate development and disease. Differential DNA methylation might play a role in these processes. In the teleost Xiphophorus, a well-established animal model for melanoma formation, tumour-specific hypomethylation of the melanoma-inducing gene ONC-Xmrk has been observed. We have isolated a cDNA for the DNA-(cytosine-5)-methyltransferase XDNMT-1 from this organism, whi ch encodes the first full-length protein from a fish species. Linkage analy sis showed that Xdnmt-1 is different from the Xiphophorus tumour suppressor R, which is involved in the transcriptional repression of the ONC-Xmrk mel anoma oncogene in healthy fish. As methylation has been implicated in the r egulation of ONC-Xmrk expression, XDNMT-1 might play a role by acting up- o r downstream of R. Expression analysis demonstrated that the Xdnmt-1 transc ript is present in all adult tissues and cell lines tested. However, develo ping embryos show a spatially and temporally regulated expression pattern s uggesting that the enzyme might play a role during development in fish. (C) 2000 Elsevier Science B.V. All rights reserved.