Genome complexity: new histone code (Introduction)

by David Turell , Friday, March 14, 2014, 17:22 (3908 days ago) @ David Turell

Add another level of coding, how cells are differentiated into many types; a histone code:
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Proper site: -http://phys.org/news/2014-03-unraveling-mystery-histone-code-gene.html--"Scientists have discovered a new mechanism that protects active genes from being silenced during cell division. They found that two variants of the same protein can distinguish active and inactive areas of the genome. The two variants differ by just one amino acid, circled here. Researchers captured the atomic structure of the two variants using a kind of molecular photography, shown here. They discovered that the single amino acid change is recognized by an enzyme (in red and blue here) that adds a silencing mark to only one variant (indicated with an arrow), instructing the cell to keep those areas of the genome inactive. Credit: Dr. Robert Martienssen, Cold Spring Harbor Laboratory -"Every cell in our body has exactly the same DNA, yet every cell is different. A cell's identity is determined by the subset of genes that it activates. But how does a cell know which genes to turn off and which to turn on? While the genetic code carried in our DNA provides instructions for cells to manufacture specific proteins, it is a second code that determines which genes are in fact activated in particular cell types.-"This second code is carried by proteins that attach to DNA. The code-carrying proteins are called histones. Today, researchers at Cold Spring Harbor Laboratory (CSHL) and colleagues publish research revealing a new layer of complexity in the histone code. They have found that the slightest variation in a single histone protein can have dramatic effects on how the genes encoded in our DNA are used.
 
"Histones are vitally important because our genetic material is vast: every cell in the body has more than six feet of DNA bundled within a tiny nucleus, a space much smaller than can be seen with the naked eye. For such a massive amount of DNA to be compacted into a microscopic space, it must be wound tightly around spool-like assemblies of proteins. Each of those spools is made up of eight histone proteins. It takes millions of spools in every cell to bundle the entire genome."