Centromeres cross over, a lot

Jun 12, 2008

Recombination at centromeres is higher than anywhere else on the chromosome, even though methyltransferases do their best to prevent it, say Jaco et al., as published in the June 16 issue of the Journal of Cell Biology.

Centromeric recombination has been hard to study because the DNA at centromeres is so repetitive—it's hard to see when a segment has switched chromatids. Jaco et al. have now addressed this challenge by using CO-FISH (chromosome orientation fluorescence in situ hybridization).

After replication, the two new strands are digested away, leaving the two old strands. Because the strands are complementary in sequence, they can be tagged with strand-specific fluorescent probes. Using just one probe, only one chromatid would show a signal if no recombination had occurred.

Instead, the authors found that both chromatids fluoresced. And not just at one point—on average, the authors counted, centromeres had undergone 15 recombination events. This is about six times the rate of recombination as that seen for an equal length of telomeric DNA, and 175 times the rate for genomic DNA as a whole.

Telomeric recombination is inhibited by protein complexes called shelterins and by DNA methylation. The centromere has no shelterin, but it is methylated. Knockdown of DNA methyltransferases increased recombination at the centromere by about 50%, and decreased centromere length, possibly because of misalignment between repeated segments during recombination, a common problem with repetitive DNA. How methylation limits recombination, and why centromeres didn't lengthen as well as shorten, are unknown.

Their repetitive structure makes centromeres recombinogenic by nature, and the authors suggest that epigenetic regulation may ensure the continued stability of essential binding regions for proteins that link to the centromere.

Citation: Jaco, I., et al. 2008. J. Cell Biol. doi:10.1083/jcb.200803042.

Source: Rockefeller University

Explore further: Study finds marine protected areas inadequate for protecting fish and ocean ecology

add to favorites email to friend print save as pdf

Related Stories

Plant models for crop breeding of the future

Jun 25, 2014

Minichromosomes have been extensively used as tools for revealing the functional structures of eukaryotic chromosomes. In the most popular model plant, Arabidopsis thaliana, however, only six different minichromosomes ...

Dual systems key to keeping chromosomes intact

Mar 07, 2013

USC scientists have discovered how two different structural apparatuses collaborate to protect repetitive DNA when it is at its most vulnerable – while it is being unzipped for replication.

In praise of the Y chromosome

Apr 20, 2010

(PhysOrg.com) -- David Page, director of the Whitehead Institute and professor of biology at Massachusetts Institute of Technology, says research indicates the much-maligned Y chromosome plays a more critical ...

PLoS Genetics 2009 maize genome collection

Nov 19, 2009

Maize is an important crop in many countries of the world. It is widely used for human consumption, animal feed, and industrial materials. It also is considered an exemplar plant species for studying domestication, molecular ...

Recommended for you

New tool aids stem cell engineering for medical research

6 hours ago

A Mayo Clinic researcher and his collaborators have developed an online analytic tool that will speed up and enhance the process of re-engineering cells for biomedical investigation. CellNet is a free-use Internet platform ...

User comments : 0