Human genome further unravelled

A close-up view of the human genome has revealed its innermost workings to be far more complex than first thought.
The study, which was carried out on just 1% of our DNA code, challenges the view that genes are the main players in driving our biochemistry.  Instead, it suggests genes, so called junk DNA and other elements, together weave an intricate control network.  The work, published in the journals Nature and Genome Research, is to be scaled up to the rest of the genome.

Views transformed

The Encyclopaedia of DNA Elements (Encode) study was a collaborative effort between 80 organisations from around the world.  It has been described as the next step on from the Human Genome Project, which provided the sequence for all of the DNA that makes up the human species’ biochemical “book of life”.

We are now seeing the majority of the rest of the genome is active to some extent.  Ewan Birney, from the European Molecular Biology Laboratory’s European Bioinformatics Institute, led Encode’s analysis effort. He told the BBC: “The Human Genome Project gave us the letters of the genome, but not a great deal of understanding. The Encode project tries to understand the genome.”

The researchers focussed on 1% of the human genome sequence, carrying out 80 different types of experiments that generated more than 600 million data points.

The surprising results, explained Tim Hubbard from the Wellcome Trust Sanger Institute, “transform our view of the genome fabric”.

Written in the DNA are genes which cells use as starting templates to make proteins; these sophisticated molecules build and maintain our bodies.  Previously, genome activity was thought of in terms of the 22,000 genes that make proteins – the functional building blocks in our cells – along with patches of DNA that control, or regulate, the genes.

The other 97% or so of the genome was said to be made up of “junk” DNA – so called because it had no known biological function.  However, junk DNA may soon need a new moniker.  Dr Hubbard said: “We are now seeing the majority of the rest of the genome is active to some extent.”

He explained that the study had found junk DNA was being transcribed, or copied, into RNA – an active molecule that relays information from DNA to the cellular machinery.  He added: “This is a remarkable finding, since most prior research suggested only a fraction of the genome was transcribed.”

‘Complex picture’

Dr Birney added that many of the RNA molecules were copying overlapping sequences of DNA.  He said: “The genome looks like it is far more of a network of RNA transcripts that are all collaborating together. Some go off and make proteins; [and] quite a few, although we know they are there, we really do not have a good understanding of what they do.

“This leads to a much more complex picture.”

The researchers now hope to scale up their efforts to look at the other 99% of the genome.  By finding out more about its workings, scientists hope to have a better understanding of the mechanics of certain diseases.  Dr Birney said that in the future, they would hope to combine their findings with some of the larger studies that are currently investigating genes known to be associated with particular conditions.  He added: “As we understand these things better, we get better insight into disease, and when we get better insight into disease, we get better insight into diagnosis and the chances to create new drugs.”