Genome complexity: more epigenetic coding sites found (Introduction)

by David Turell , Monday, December 21, 2015, 20:53 (3047 days ago) @ David Turell

Most methylation occurs on cytosine , but some is now found an adenine:-http://www.sciencedaily.com/releases/2015/12/151221133734.htm-"Epigenetics has so far focused mainly on studying proteins called histones that bind to DNA. Such histones can be modified, which can result in genes being switched on or of. In addition to histone modifications, genes are also known to be regulated by a form of epigenetic modification that directly affects one base of the DNA, namely the base C. More than 60 years ago, scientists discovered that C can be modified directly through a process known as methylation, whereby small molecules of carbon and hydrogen attach to this base and act like switches to turn genes on and off, or to 'dim' their activity. Around 75 million (one in ten) of the Cs in the human genome are methylated.-"Now, researchers at the Wellcome Trust-Cancer Research UK Gurdon Institute and the Medical Research Council Cancer Unit at the University of Cambridge have identified and characterised a new form of direct modification -- methylation of the base A -- in several species, including frogs, mouse and humans.-"Methylation of A appears to be far less common that C methylation, occurring on around 1,700 As in the genome, but is spread across the entire genome. However, it does not appear to occur on sections of our genes known as exons, which provide the code for proteins.-"'These newly-discovered modifiers only seem to appear in low abundance across the genome, but that does not necessarily mean they are unimportant," says Dr Magdalena Koziol from the Gurdon Institute. "At the moment, we don't know exactly what they actually do, but it could be that even in small numbers they have a big impact on our DNA, gene regulation and ultimately human health.'"-Comment: It means, s ENCODE research showed, less and less junk.