Mouse Work: New Insights on a Fundamental DNA Repair Mechanism

Mar 02, 2010
New research on a house mouse enzyme, Mus musculus NEIL3, sheds new light on a fundamental DNA respair mechanism. Image ©Toenne/courtesy Shutterstock

(PhysOrg.com) -- Adding a new link to our understanding of the complex chain of chemistry that keeps living cells alive, a team of researchers from the University of Vermont (UVM), the University of Utah, Vanderbilt University and the National Institute of Standards and Technology has demonstrated for the first time the specific activity of the protein NEIL3, one of a group responsible for maintaining the integrity of DNA in humans and other mammals. Their work reported last week sheds new light on a potentially important source of harmful DNA mutations.

Since it first was identified about eight years ago, NEIL3 has been believed to be a basic DNA-maintenance enzyme of a type called a glycosylase. These proteins patrol the long, twisted strands of looking for —places where one of the four DNA bases has been damaged by radiation or chemical activity. They cut the damaged bases free from the DNA backbone, kicking off follow-on mechanisms that link in the proper undamaged base. The process is critical to cell health, says NIST biochemist and Senior Research Fellow Miral Dizdaroglu, “DNA is damaged all the time. About one to two percent of oxygen in the body becomes toxic in cells, for example, creating that damage DNA. Without these DNA repair mechanisms there wouldn’t be any life on this planet, really.”

The glycosylases seem to be highly specific; each responds to only a few unique cases of the many potential DNA base lesions. Figuring out exactly which ones can be challenging. NEIL3 and its kin NEIL1 and NEIL2 are mammalian versions of an enzyme found in the E. coli, which first was identified in work at UVM. The lesion targets of NEIL1 and NEIL2 have been known for some time, but NEIL3, a much more complicated protein twice the size of the others, had resisted several attempts to purify it and determine just what it does. In a significant advance, a research team at UVM managed to clone the house version of NEIL3 (99 percent identical to the human variant), and then prepare a truncated version of it that was small enough to dissolve in solution for analysis but large enough to retain the portion of the protein that recognizes and excises DNA lesions.

Using a technique they developed for rapidly analyzing such enzymes, NIST researchers Dizdaroglu and Pawel Jaruga mixed the modified protein with sample DNA that had been irradiated to produce large numbers of random base lesions. Because glycosylases work by snipping off damaged bases, a highly sensitive analysis of the solution after the DNA has been removed can reveal just which lesions are attacked by the enzyme, and with what efficiency. The NIST results closely matched independent tests by others in the team that match the enzyme against short lengths of DNA-like strands with a single specific target lesion.

In addition to finally confirming the glycosylase nature of NEIL3, says UVM team leader Susan Wallace, tests of the enzyme in a living organism—a tailored form of E. coli designed to have a very high mutation rate—had an unexpected bonus. Measurements at NIST showed that NEIL3 is extremely effective at snipping out a particular type of lesion called FapyGua (2,6-diamino-4-hydroxy-5-formamidopyrimidine) and seems to dramatically reduce mutations in the bacterium, a result that points both to the effectiveness of NEIL3 and the potentially important role of FapyGua in causing dangerous mutations in DNA.

Explore further: Micro fingers for arranging single cells

More information: M. Liu, V. Bandaru, J.P. Bond, P. Jaruga, X. Zhao, P.P. Christov, C.J. Burrows, C.J. Rizzo, M. Dizdaroglu and S.S. Wallace. The mouse ortholog of NEIL3 is a functional DNA glycosylase in vitro and in vivo. Proc. Natl. Acad. Sci. USA, Early Edition, Published online before print Feb. 25, 2010, doi:10.1073/pnas.0908307107

Related Stories

Links Between DNA Damage and Breast Cancer Studied

Aug 03, 2006

Researchers from the Pacific Northwest Research Institute (PNRI) and the National Institute of Standards and Technology (NIST) have uncovered a pattern of DNA damage in connective tissues in the human breast that could shed ...

DNA size a crucial factor in genetic mutations, study finds

Oct 26, 2005

Researchers at Stanford University have created a larger-than-normal DNA molecule that is copied almost as efficiently as natural DNA. The findings, reported in the Oct. 25 online edition of the Proceedings of the National Ac ...

New Method Offers Insight into Radiation Damage to DNA

Mar 21, 2008

A new technique for assessing the damage radiation causes to DNA indicates that the spatial arrangement of damaged sites, or lesions, is more important than the number of lesions in determining the severity ...

Recommended for you

Micro fingers for arranging single cells

22 hours ago

Functional analysis of a cell, which is the fundamental unit of life, is important for gaining new insights into medical and pharmaceutical fields. For efficiently studying cell functions, it is essential ...

Detailed structure of human ribosome revealed

Apr 24, 2015

A team at the Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC - CNRS/Université de Strasbourg/Inserm) has evidenced, at the atomic scale, the three-dimensional structure of the complete ...

How to kill a protein

Apr 24, 2015

For decades scientists have been looking closely at how our cells make proteins. But the inverse is equally important: how cells kill them.

How RNA machinery navigates our genomic obstacle course

Apr 24, 2015

Once upon a time, scientists thought RNA polymerase—the molecule that kicks off protein synthesis by transcribing DNA into RNA—worked like a wind-up toy: Set it down at a start site in our DNA and it ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.