It\u2019s a common storytelling trope: the stubborn foe who is eventually revealed to be a much-needed friend.\u00a0<\/p>\n
Biology has its own version. Cornell researchers have discovered that DNA packaging structures called nucleosomes, which have been traditionally seen as roadblocks for gene expression, actually help reduce torsional stress in DNA strands and facilitate the decoding of genetic information.<\/p>\n
\u201cIf gene expression does not proceed properly, it will lead to all kinds of problems. Abnormal cellular growth, cancer development and other disorders \u2013 they’re all interconnected,\u201d said\u00a0Michelle Wang<\/a>, the James Gilbert White Distinguished Professor of the Physical Sciences in the College of Arts and Sciences, who led the project. \u201cGene expression is at the heart of the central dogma of biology, and how that\u2019s regulated dictates everything that\u2019s coming downstream. I think we\u2019re filling in a piece of the puzzle for something really fundamental that affects so many things.\u201d<\/p>\n The findings were published Dec. 18<\/a> in Science. The lead author is postdoctoral researcher Jin Qian, Ph.D. \u201923.<\/p>\n Transcription \u2013 a crucial step of gene expression \u2013 is a knotty process with a lot of moving parts, all of which are essential for any kind of cellular function. That\u2019s because DNA essentially serves as the instruction manual for genes, and that information must be decoded, copied and then disseminated via RNA.\u00a0<\/p>\n But there\u2019s a twist. DNA\u2019s helical structure creates a problem similar to what happens when you try to unwind a tightly coiled rope: the more you unwind one section, the tighter the rest becomes. That\u2019s what happens during transcription, as the motor enzyme RNA polymerase twists the DNA and slowly moves along it, copying the code. It\u2019s not a smooth journey. The polymerase\u2019s progression is hindered by nucleosomes, the basic packing units of DNA that make up chromatin. Not only must the polymerase overcome these obstacles, it must also rotate to track the DNA helix. These rotations supercoil the DNA and generate torsional stress, which acts as another obstacle. Yet somehow the process succeeds.<\/p>\n