A skeleton for chromosomes

Aug 26, 2013
A Skeleton for Chromosomes
Artistic interpretation of fluorescent light micrographs of Wapl depleted nuclei which show cohesin vermicelli. The nuclei have been pseudo-colored and scaled to different sizes. Credit: IMP

Researchers at the IMP Vienna discovered that cohesin stabilizes DNA. Jan-Michael Peters and his team at the Research Institute of Molecular Pathology (IMP) found that the structure of Chromosomes is supported by a kind of molecular skeleton, made of cohesin. Their discovery is published in the forthcoming issue of the journal Nature.

Every single cell in the human body contains an entire copy of the , the DNA. Its total length is about 3.5 meters and all of it has to fit into the cell's nucleus, just one-hundredth of a millimeter in diameter. Blown up in proportion, this would equal the task of squeezing a 150km long string into a soccer ball. Just how the cell manages to wrap up its DNA so tightly is still poorly understood.

One way of compacting DNA is achieved by coiling it tightly around . This mechanism has been studied in detail and is the focus of an entire discipline, Epigenetics. However, simple organisms such as bacteria have to manage their DNA-packaging without histones, and even in histones probably cannot do the job on their own.

A new role for an old molecule

A team of scientists at the Research Institute of Molecular Pathology (IMP) in Vienna can now present evidence for an additional mechanism involved in structuring DNA. Managing Director Jan-Michael Peters and his research group discovered that a protein-complex named cohesin has a stabilizing effect on DNA. In evolutionary terms, cohesin is very old and its structure has hardly changed over billions of years. It was present long before and might therefore provide an ancient mechanism in shaping DNA.

Cell biologists are already familiar with cohesin and its role in cell division. The protein-complex is essential for the correct distribution of chromosomes to . It forms a molecular ring that keeps sister-chromatids together until the precise moment when segregation takes place. This function and the of cohesin have been discovered by IMP-scientists in 1997.

Antonio Tedeschi, a postdoc in the group of Jan-Michael Peters, has now found evidence that cohesin supports the architecture of DNA in non-dividing (interphase) cells. He analyzed cells in which he had shut down the function of Wapl. This protein controls how tightly cohesin binds to DNA. Without Wapl, cohesin is 'locked' onto chromatin in an unusually stable state. As a consequence, cells are unable to express their genes correctly and cannot divide.

Vermicelli keep DNA in shape

When he analyzed Wapl-depleted cells under the microscope, Tedeschi found elongated structures that he called "vermicelli" (Italian for small worms). Since one vermicello is present for each chromosome, he concluded that its function is to keep chromosomes in shape, rather like a skeleton.

"We think that the vermicelli are the 'bones' of interphase chromosomes", says Jan-Michael Peters. "Just like our bodies depend on the bones for support, the depend very much on cohesin to retain their structure."

The importance of the cohesin-system becomes obvious in cases where it is impaired. Several rare congenital diseases have been linked to mutations in the respective gene. The faulty structure of the cohesin molecule causes severe developmental retardation and is a serious medical condition. There are no causal therapies available at present.

Explore further: Cell memory mechanism discovered

More information: Tedeschi, A. et al. Wapl is an essential regulator of chromatin structure and chromosome segregation, Nature. DOI: 10.1038/nature12471

add to favorites email to friend print save as pdf

Related Stories

Cell memory mechanism discovered

Aug 15, 2013

The cells in our bodies can divide as often as once every 24 hours, creating a new, identical copy. DNA binding proteins called transcription factors are required for maintaining cell identity. They ensure that daughter cells ...

Cohesin jigsaw begins to fit

May 19, 2009

The essential chromosomal protein complex cohesin has crucial roles in sister chromatid cohesion, DNA repair and transcriptional regulation. Despite its conserved function, cohesin's disparate association patterns in different ...

Shaping up for cell division

Nov 04, 2011

The shape of chromosomes is determined by the relative levels of key protein complexes, research conducted by Keishi Shintomi and Tatsuya Hirano of the RIKEN Advanced Science Institute has shown.

Chromosome 'glue' surprises scientists

May 06, 2010

Proteins called cohesins ensure that newly copied chromosomes bind together, separate correctly during cell division, and are repaired efficiently after DNA damage. Scientists at the Carnegie Institution have found for the ...

Surprise in genome structure linked to developmental diseases

Aug 18, 2010

A team of researchers from Whitehead Institute, MIT, University of Colorado, and University of Massachusetts have discovered that each cell type in our bodies has a unique genome structure, which is due to a newly discovered ...

Recommended for you

For resetting circadian rhythms, neural cooperation is key

2 hours ago

Fruit flies are pretty predictable when it comes to scheduling their days, with peaks of activity at dawn and dusk and rest times in between. Now, researchers reporting in the Cell Press journal Cell Reports on April 17th h ...

Rapid and accurate mRNA detection in plant tissues

4 hours ago

Gene expression is the process whereby the genetic information of DNA is used to manufacture functional products, such as proteins, which have numerous different functions in living organisms. Messenger RNA (mRNA) serves ...

For cells, internal stress leads to unique shapes

22 hours ago

From far away, the top of a leaf looks like one seamless surface; however, up close, that smooth exterior is actually made up of a patchwork of cells in a variety of shapes and sizes. Interested in how these ...

Adventurous bacteria

23 hours ago

To reproduce or to conquer the world? Surprisingly, bacteria also face this problem. Theoretical biophysicists at Ludwig-Maximilians-Universitaet (LMU) in Munich have now shown how these organisms should ...

User comments : 0

More news stories

Fear of the cuckoo mafia

If a restaurant owner fails to pay the protection money demanded of him, he can expect his premises to be trashed. Warnings like these are seldom required, however, as fear of the consequences is enough to ...

Clean air: Fewer sources for self-cleaning

Up to now, HONO, also known as nitrous acid, was considered one of the most important sources of hydroxyl radicals (OH), which are regarded as the detergent of the atmosphere, allowing the air to clean itself. ...

Turning off depression in the brain

Scientists have traced vulnerability to depression-like behaviors in mice to out-of-balance electrical activity inside neurons of the brain's reward circuit and experimentally reversed it – but there's ...

Thinnest feasible nano-membrane produced

A new nano-membrane made out of the 'super material' graphene is extremely light and breathable. Not only can this open the door to a new generation of functional waterproof clothing, but also to ultra-rapid filtration. The ...