'Anchors' Organize chromosomal DNA during cell division

'Anchors' Organize chromosomal DNA during cell division: New role of telomeres in cell growth may shed light on aging and age-related diseases

For humans to grow and to replace and heal damaged tissue, the cells of the body must play continuously, a process known as "cell division", by which a cell becomes two, two become four, and so successively. A key question is how bio-medical research chromosomes that are duplicated during cell division so that each daughter cell receives an exact copy of the genome of a person, are organized during this process.
Now, scientists at the Salk Institute have discovered a new function of human cell division that can help explain how DNA is organized in the nucleus of cells reproduce. They found that telomeres, molecular caps protect the ends of chromosomes move toward the outer edge of the cell nucleus after they have been duplicated.
This image shows the telomeres (yellow), protective caps on the ends of chromosomes that have been moved to the outer edge of a cell nucleus (blue). Salk researchers discovered that anchor telomeres to the nuclear membrane after the cell duplicates its DNA during cell division, which can help organize chromosomes as the cell divides into two daughter cells.
While the consequences of this spatial reorganization of telomeres are not yet clear, the findings could shed light on how our genes are regulated and how programs are altered gene expression during cell division, an important step in understanding the aging and diseases arising from genetic mutations, such as cancer.
"What we have discovered is that telomeres not only protect our chromosomes, also help organize our genetic material in the nucleus," says Jan Karlseder, a professor in the Salk Laboratory of Molecular and Cellular Biology and Darlene Shiley President and Donald. "This is important, because the three-dimensional position of the DNA in the nucleus influences gene expression profiling and how it changes over time in the genome."
Telomeres, a combination of protein and DNA are vital in DNA replication aging and tumor suppression. Whenever a primary human cell divides, the telomeres shorten until critically short telomeres lead to cell destruction. Much research has been focused on understanding the dynamics Karlseder telomeres to develop ways to influence the aging process, and thus limit the growth of cancer cells.
Besides explore the involvement of telomeres in aging syndromes and interactions between the mechanism of DNA damage and telomere Karlseder studies the role of telomeres during cell cycle. Previous studies on human cells have shown that telomeres change position during cell division, suggesting that also may play a role in the organization of the DNA into nuclei. However, these studies only provide instant telomeres isolated at different stages of the cell cycle.
In their new study, the researchers used advanced time lapse confocal microscopy Salk live cells to track the movement of telomeres in real time during the cell cycle. Continued for 20 hours telomeres in living cells molecules by labeling with bright under a microscope. They also recorded the movement of chromatin, a combination of DNA and proteins that form chromosomes.

The scientists found that telomeres moved to the outer periphery of the nuclear envelope of each daughter cell nucleus as meet after mitosis, cell division stage during which doubles the cell's DNA to provide each cell daughter with her own copy. By exploring the underlying molecular pathways, the researchers determined that the interaction between two proteins, RAP1 and Sun1, telomeres appear to bind to the nuclear envelope. Sun1 alone was also able to attract nuclear envelope telomeres, which suggests that the protein is essential for the process and the other elements that might be able to replace RAP1 during immobilization.
"Immobilization of telomeres to the nuclear envelope can serve as an anchor for the reorganization of chromatin after each cell division, so that our DNA is well placed for gene expression," says Karlseder. "This immobilization could also play a role in the maintenance of telomeres, which influences aging, the development of cancer and other disorders associated with DNA damage. We intend to explore these possibilities in future experiments."
Other researchers at the Salk Institute in the paper were Laure Crabbe, Anthony J. Caesar and James M. James Fitzpatrick and AJ Kasuboski Fund Waitt Advanced Biophotonics Center Core.