For a skin cell to do its job, it must turn on a completely different set of genes than a liver cell -- and keep genes it doesn't need switched off. One way of turning off large groups of genes at once is to send them to "time-out" at the edge of the nucleus, where they are kept quiet. New research from Johns Hopkins sheds light on how DNA gets sent to the nucleus' far edge, a process critical to controlling genes and determining cell fate. A report on the work appeared in the Jan. 5 issue of the Journal of Cell Biology. "We discovered a DNA sequence and a specific set of protein tags that send DNA to the edge of the nucleus, where its genes get turned off," says Karen Reddy, Ph.D., an assistant professor of biological chemistry at the Johns Hopkins University School of Medicine. Picture the nucleus as a round room filled with double strands of DNA hanging in suspension as they are opened, closed, clipped, patched and read by proteins that come and go. At the edge of the nucleus, just inside its flexible walls, the lamina meshwork provides shape and support. But accumulating evidence … Continue reading →

IMAGE:In mouse cells, the YY1 protein binds to a segment of DNA (green), leading it to attach to the lamina (red) at the edge of the nucleus. view more Credit: Reddy Lab, Johns Hopkins Medicine For a skin cell to do its job, it must turn on a completely different set of genes than a liver cell -- and keep genes it doesn't need switched off. One way of turning off large groups of genes at once is to send them to "time-out" at the edge of the nucleus, where they are kept quiet. New research from Johns Hopkins sheds light on how DNA gets sent to the nucleus' far edge, a process critical to controlling genes and determining cell fate. A report on the work appeared in the Jan. 5 issue of the Journal of Cell Biology. "We discovered a DNA sequence and a specific set of protein tags that send DNA to the edge of the nucleus, where its genes get turned off," says Karen Reddy, Ph.D., an assistant professor of biological chemistry at the Johns Hopkins University School of Medicine. Picture the nucleus as a round room filled with double strands of DNA hanging in suspension as … Continue reading →

Since the discovery of how DNA encodes genetic information, most research on the evolution of life has focused on genes. According to the "selfish gene" theory, cells and organisms exist simply as packages to protect and transmit genes. New research challenges this idea, proposing instead that if anything is "selfish" it must be the ribosome. That up-ends everything we think we know about the evolution of life and, in fact, the function of ribosomes themselves. What came first in the evolution of life? Until now, scientists have answered the question with three letters: DNA. But In a father-daughter collaboration published in Journal of Theoretical Biology, Dr. Meredith Root-Bernstein, Aarhus University, Denmark, and Dr. Robert Root-Bernstein, Michigan State University, USA, provide evidence that the question should rather be answered with the word: Ribosomes. The ribosome is a large and complex molecule found in all living cells. It contains the machinery for translating the genetic information from DNA into the proteins that perform all the work of the cell and make up most of its structure. "Ribosomes are made of three protein-encrusted RNA strands that textbooks tell us are purely structural, but we show that ribosomal RNA once acted as the genes, … Continue reading →