Tuesday, November 25, 2008

Accessing DNA and Kissing Ass

Scripps Research scientists shed light on how DNA is unwound so that its code can be read is a Biology News Net article. Discussed is a macromolecular machine, dubbed RSC, which is able to alter chromatin so as to allow enzyme access and resultant gene expression. Researchers from The Scripps Research Institute have discovered how this is done. They published their findings in the November 23, 2008 online issue of Nature Structural & Molecular Biology.

RSC is a very large protein complex consisting of thirteen different proteins. Its signature property is a capacity to hold individual nucleosomes in what the author describes as what looks like a vise grip. Nucleosomes are subunits of chromatin. Chromatin consists of a DNA coiled around a core of proteins known as histones. Chromatin plays an important role in regulating gene expression. Whether a gene, coding for a particular protein, is transcribed depends on the capacity of enzymes, involved in the transcription function, to access the gene. Chromatin can prevent access. RSC can reverse that condition. RSC activity requires an input of energy supplied by ATP.

The article concludes (quoting):

The structure RSC interacting with a nucleosome explains how previously observed DNA bulges formed by chromatin remodeling complexes are formed, and why a single intact nucleosome appears to be left on a fully activated gene before other cellular machinery scoop up the histones and repack the DNA until it needs to be read again.

"Every time your cell expresses a gene, it goes through this remarkable unpacking and repacking," he says. "We are happy to have provided some clarity to the process."

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PS: One of my uncles sent me this poem:

No Hard Feelings...to the democrats
The election day is over,
The talking is done.
My party lost, your party won.
So let us be friends,
Let arguments pass.
I'll hug my elephant,
You kiss your ass.

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