Mouse Work: New Insights on a Fundamental DNA Repair Mechanism

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

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 (NIST) 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 DNA looking for lesions—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 free radicals 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 bacterium 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 mouse 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** 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.

* 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.

** 2,6-diamino-4-hydroxy-5-formamidopyrimidine

Media Contact: Michael Baum, michael.baum@nist.gov, (301) 975-2763

Comments

[sankaravelayudhan nandakumar]

Better resaerch could be made with simian monkey's brainusing biometric study of palm print on humanbeingsas comprator for DNA corrections:
Clubbed thumb with twisted brainline shows abnormal aggressiveness requiring investigation -reg
Dr.Meyer from Chicago was caught for poisoning his patient and in his case the brain line was twisted from its usual place by cutting through the heart line. Some reporters representing Newyork world called and tested the power of Cheiro by having him read imprints of hand without him knowing the names and positions of any of the people.
Cheiro had described the character and careers of dozens of these test cases ,when an impression of a strange looking pair of hands were put before him.Cheiro was struck by the fact that the brain line on the left was normal while the on the right were abnormal twisted out of its place.
Cheiro said by summing up this impression of brain line that this man would have got the change in his tendency under the continual urge to acquire wealth at any cost ,a criminal tendency until he was finally prepared even to commit murder.The oxford astrogeneticist are of the opinion that more agresiveness could be found on a man with clubbed thumb which brain line twisted from its normal place. If the Venus mount is more aggressive a biometric study will reveal the crime may be due to aggressive sex demand especially on plam print without a heartline at all.
Clubbed thumb shows increased aggressive behavior (Becker et al 1999), again suggesting a neuro developmental link between hippocampal abnormalities and aggression Normal hippocampal functioning is critical for the retrieval of emotional memories and contextual fear conditioning requiring investigation in clubbed thumb. In contrast, successful psychopaths who lack hippocampal impairments may have relatively normal contextual fear conditioning, making them more sensitive to cues predicting capture. Similarly, LeDoux (1996) has suggested that uncoupling of the hippocampus from the amygdale could result in the expression of emotions that are inappropriate to the social context and also in poor insight into emotional states, a perspective consistent with clinical features of caught psychopaths. Interestingly, a PET study of humans indicates that unpleasant emotions activate the left but not right hippocampus (Lane et al 1997), a finding conceptually consistent with the notion that unsuccessful psychopaths have relatively reduced left hippocampal structure and also reduced autonomic reactivity to a social emotional stressor (Ishikawa et al 2001).
The anterior hippocampal asymmetries may be associated with unsuccessful psychopathy by signaling disruption to frontal-subcortical neural circuitry. In humans, the orbitofrontal cortex likely exerts control over the anterior hippocampus through entorhinal-hippocampal projections (Pansky et al 1988; Stuss and Benson 1986), whereas afferent connections have been mapped between the subiculum and ventral, dorsolateral, and rostral regions of the prefrontal cortex in cats (Scannell et al 1995).
Animal research has also found that lesions to the septal-hippocampal-frontal system result in behavioral disinhibition and a hypersensitivity to immediate reward (Gorenstein and Newman 1980). Disruption to circuits involving the prefrontal cortex and hippocampus have been implicated in both disrupted emotion regulation and antisocial–aggressive behavior (Davidson 2000; Davidson et al 2000; Hoptman et al 2002; Raine 2002; Raine et al 2000), whereas frontal and executive function deficits are frequently identified in institutionalized psychopathic and antisocial individuals (Moffitt 1993b; Raine et al 1998). Prior research with the present sample has found that unsuccessful psychopaths demonstrate executive dysfunction compared with successful psychopaths (Ishikawa et al 2001), and hippocampal abnormalities may be most likely to predispose to aggressive, inappropriate, and psychopathic behavior when combined with prefrontal impairments that decrease behavioral inhibition. Disruption to prefrontal-hippocampal circuitry could therefore result in impulsive, disinhibited, unregulated, and reward-driven antisocial behavior that is more prone to legal detection in the unsuccessful psychopath, but further workis needed to verify such prefrontal involvement in unsuccessful psychopaths.
Sankara Velayudhan Nandakumar,astrogeneticist along with Dr.James E. Rothman, Ph.D., the Fergus F. Wallace Professor of Biomedical Sciences and chair of the medical school’s Department of Cell Biology, Hon. Sir J.Pendry F.R.S of imperial college uk special officer on combustion nano technology along with Dr.GANESAN ,IIT professor ,combustion dept Cape Institute of Technology,Nagercoil formerly with ,KNSK Engineering college ,Nagercoil as research scholar,Anna University with Hubble space research committee of Hon.Roger Davies,Hon.Collin Webbs FRS of Laser dn of Oxford uk,Hon.Marteen Rees ,Emeritus Professor of cosmology Cambridge ,former president of Royal society, London.
Sankara Velayudhan Nandakumar member PNAS ,American ,JILA,NIST Group member on behalf of Cape Institute of technology Energy system dept Loyola college of Engineering and technology ,Member American committee for the Weizman institute of science ,Energy renovation committee cape Institute of Technology,Nagercoil ,former Guest lecturer ,KNSK Enginering college ,Anna University have surprisingly found out genetic mirror
1) Clubbed thumb with twisted brainline shows abnormal aggressiveness requiring investigation -reg [Incident: 100825-000078 news@nature.com"

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