The expression of genes that help to limit the growth of normal cells can sometimes be turned down in cancer, causing cells to divide uncontrollably - hence their branding as 'tumour suppressor' genes. Previously, this -silencing - of gene expression was shown to result from changes in a particular methylation modification of the DNA encoding tumour suppressor genes, but puzzlingly, no mutations had been found in the enzymes that carry out methylation. A paper in Nature resolves this conundrum by identifying an RNA agent inside the cell nucleus that is able to tamper with the expression of one such gene, p15, which is silenced in leukaemia and other cancers.
Andrew Feinberg and colleagues pinpointed the rogue RNA because of its 'antisense' pattern of bases, which are a match with those of p15's DNA. They worked out a molecular mechanism to explain how this antisense RNA effectively manages to silence both copies of the gene present in the cell, leaving it stripped of its protection against unregulated growth. This seems to be a general mechanism, as many tumour suppressor genes are found to have nearby antisense RNAs. This seems to be a general mechanism, as many tumour suppressor genes are found to have nearby antisense RNAs.
Andrew Feinberg (Johns Hopkins University School of Medicine, Baltimore, MD, USA)
(C) Nature press release.
Message posted by: Trevor M. D'Souza
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