Новое в изучении репарации ДНК

Процесс репарации ДНК зафиксирован! Информация с http://www.eurekalert.org/pub_releases/2009-01/uoc--hdr012809.php по ссылке есть картинка и видео для заинтересовавшихся. :)

Contact: Liese Greensfelder
University of California - Davis
Human DNA repair process recorded in action
Fluorescent microscopy captures the repair protein Rad51 as it assembles into a filament on DNA

A key phase in the repair process of damaged human DNA has been observed and visually recorded by a team of researchers at the University of California, Davis. The recordings provide new information about the role played by a protein known as Rad51, which is linked to breast cancer, in this complex and critical process.

The breakthrough comes a decade after Stephen Kowalczykowski, a distinguished professor of microbiology and the study's principal investigator, and Ron Baskin, professor emeritus of molecular and cellular biology, first began developing methods of labeling molecules with fluorescent markers and observing them at work using optical trapping of individual DNA molecules and advanced microscopy techniques. In 2006, the researchers recorded a portion of the bacterial DNA repair process, a system considerably less complex than its human counterpart. The new study was published in the Proceedings of the National Academy of Sciences on Jan. 13.

Human DNA is under constant assault from harmful agents such as ultraviolet sunlight, tobacco smoke and a myriad of chemicals, both natural and man-made. Because damage can lead to cancer, cell death and mutations, an army of proteins and enzymes are mobilized into action whenever it occurs.

Rad51 takes a leading role in the action. Always on call in the cell, molecules of the protein assemble into a long filament along a damaged or broken segment of DNA, where they help stretch out the coiled strands and align them with corresponding segments on the cell's second copy of the chromosome, which serves as a template for reconstruction. Because this protein is regulated by a gene linked to increased risk of breast cancer, BRCA2, it is also thought to play a role in suppression of that disease.

With the ability to watch the assembly of individual filaments of Rad51 in real time, Kowalczykowski's team made a number of discoveries. Among those are that, in contrast to their bacterial counterparts, Rad51 filaments don't grow indefinitely. This indicates that there is an as-yet undiscovered mechanism that regulates the protein's growth, Kowalczykowski said.

Another surprising difference between the human and bacterial processes, Kowalczykowski said, is that Rad51 doesn't fall away from the DNA when repair is complete. Instead, proteins that motor along DNA are required to dislodge it.

"From a practical point of view, being able to record these single molecules gives us insightful information regarding the assembly process," the researcher said. "Now we're able to measure this in a quantifiably meaningful way."


Other contributors to the study were postdoctoral scholars Jovencio Hilario and Ichiro Amitani.

The research was supported by the National Institutes of Health and a Susan G. Komen Postdoctoral Fellowship.

The paper and supporting materials can be viewed online at http://www.pnas.org/.

About UC Davis

For 100 years, UC Davis has engaged in teaching, research and public service that matter to California and transform the world. Located close to the state capital, UC Davis has 31,000 students, an annual research budget that exceeds $500 million, a comprehensive health system and 13 specialized research centers. The university offers interdisciplinary graduate study and more than 100 undergraduate majors in four colleges -- Agricultural and Environmental Sciences, Biological Sciences, Engineering, and Letters and Science -- and advanced degrees from five professional schools: Education, Law, Management, Medicine, and Veterinary Medicine. The UC Davis School of Medicine and UC Davis Medical Center are located on the Sacramento campus near downtown.


О новом фармсредстве. Антидепрессант и лекарство от фибромиалгии

Не стоит на месте доблестная Фармацевтическая Промышленность!!! Вот, очередной препарат - http://scienceblogs.com/corpuscallosum/2009/01/milnacipran_savella_approved_f.php
Milnacipran (Savella™) Approved for Fibromyalgia

Category: Neuroscience • Science News
Posted on: January 26, 2009 8:25 AM, by Joseph j7uy5
Milnacipran (Savella™)On 14 January, 2008, the US FDA approved milnacipran for use in treatment of fibromyalgia. It is ( or soon will be) available in tablets of 12.5, 25, 50, and 100mg. It has been marketed as an antidepressant in Europe for years, but has not been available in the USA until now.

Milnacipran is a drug that inhibits reuptake of serotonin and norepinephrine. The effect on norepinephrine is stronger than the effect on serotonin. It can be thought of as an SNRI, is the same family as venlafaxine (Effexor), duloxetine (Cymbalta) and desvenlafaxine (Pristiq).

From the Savella package insert (PDF), I've copied the dosing guidelines below. Note that the initial dosing guidelines often are not quite right; it takes experience in a larger population to figure out the best dosing. The titration schedule, as proposed, has the potential to be troublesome. It is likely that they will distribute dose-packs to make the titration easier to follow.

• Administer Savella in two divided doses per day
• Begin dosing at 12.5 mg on the first day and increase to 100 mg/day over a 1-week period (2.1): Day 1: 12.5 mg once Days 2-3: 25 mg/day (12.5 mg twice daily) Days 4-7: 50 mg/day (25 mg twice daily) After Day 7: 100 mg/day (50 mg twice daily)
• Recommended dose is 100 mg/day
• May be increased to 200 mg/day based on individual patient response

For milnacipran, the kinetics are as follows: oral bioavailability is 85-90%; the extent of absorption is not affected by food; half-life is 6-8 hours; 55% percent is excreted unchanged in the urine. Note that the active enantiomer, d-milnacipran, has a longer elimination half-life (8-10 hours) than the l-enantiomer (4-6 hours). Small percentages of the parent drug are metabolized by desethylation (N-desethyl milnacipran, 8%) and glucuronidation (d- and l-milnacipran carbamoyl-O-glucuronide, 2% and 17%, respectively). Plasma protein binding is 13%. No dosage adjustment is needed for mild renal impairment, or for mild to moderate hepatic impairment. Cmax and area-under-the-curve are 30% higher for persons over 65, and 20% higher for women, but no dosage adjustment is necessary. Milnacipran did not inhibit or induce any of the cytochrome P450 enzymes listed in the PI.

Savella carries a black-box warning about suicidality, based upon its similarity to other SNRI. This is addressed in this Medication Guide (PDF).

What role will milnacipran have in the armamentarium of available treatments? As it happens, a meta-analysis was published in JAMA a couple of weeks ago: Treatment of Fibromyalgia Syndrome With Antidepressants: A Meta-analysis (JAMA. 2009;301(2):198-209) Only the abstract is openly accessible. There's a summary available on Medscape (free registration) that contains more detail than the abstract:

The researchers found that amitriptyline had a large effect on reducing pain, fatigue, and sleep disturbances, a small effect on HRQOL, and no significant effect on mood.

In addition, they found that the SSRIs fluoxetine and paroxetine had a small effect on reducing pain and improving HRQOL but had no effect on fatigue or sleep.

SNRIs duloxetine and milnacipran had a small effect on reducing pain and sleep disturbances, and duloxetine had a small effect on improving mood and HRQOL, but no effect on fatigue.

The MAOIs moclobemide and pirlindole had a small effect on pain reduction. Moclobemide had no effect on sleep or fatigue, and pirlindole did not affect depressed mood.

HRQOL=health-related quality of life.

Only one study of milnacipran was included in the analysis, so there is a lot of information that was not included. Plus, the meta-analysis isn't ideally suited to compare one drug against the others. The bottom line, though, is that amitriptyline appeared to have the biggest effect. Unfortunately, amitriptyline is more likely than the others to have burdensome adverse effects. Amitriptyline is inexpensive, $4/month in some places. I don't know what milnacipran will cost, but it will be a lot more than $4/month.

Some additional perspective can be gained from this interview with a fibromyalgia expert, Daniel J. Clauw, MD:

Q: Do you have a standardized treatment protocol for your FM patients?

Dr. Clauw: I use a combination of low-impact aerobic exercise, symptom-based pharmacologic therapy, and cognitive behavioral therapy. Not all patients need all three.

I usually begin by prescribing medications to target the two or three most prominent symptoms that a patient has. In most cases pain is one, but poor sleep, fatigue, memory problems, or other symptoms sometimes interfere more with function than pain.

I only use one treatment at a time, and see if it works before deciding whether to continue with the treatment, or discard it. One of the biggest problems I see in practice is that doctors and patients try too many things at once, and then they have limited ability to tell if something is working, or whether a new symptom is a side effect of a treatment.

After I find the correct one or two medications to reasonably control many of the symptoms, then I will add aerobic exercise, and sometimes cognitive behavioral therapy (CBT). Both exercise and CBT can either be done simply (with simple instructions for exercise or a workbook or Arthritis Foundation course for CBT) or with more professional guidance (e.g., with a physical therapist, personal trainer, social worker, or psychologist).

These treatments take many months to work (in contrast to medications, which usually work within a month or so if they are going to work at all), but the benefits are more durable than the benefits obtained from medications.

Clauw goes on to discuss specific drugs, but milnacipran is not included, since the interview is from 2007.

The main points from the interview: patients often have to try several different medications or combinations, and the medication is only part of the overall treatment. There is no single treatment that stands out as clearly superior, and there is no single treatment that eliminates the need for multimodal intervention. In such a situation, it is always nice to have another option. In my view, milnacipran is exactly that: another option. Probably it will be a great thing for some people, pretty good for others, so-so for some, and worthless for others.


О повторах и палиндромах в ДНК

Хорошая информация с http://www.biologynews.net/archives/2009/01/11/biologists_discover_link_between_cgg_repeats_in_dna_and_neurological_disorders.html

Researchers have long known that some repetitive DNA sequences can make human chromosomes "fragile," i.e. appearing constricted or even broken during cell divisions. Scientists at Tufts University have found that one such DNA repeat not only stalls the cell's replication process but also thwarts the cell's capacity to repair and restart it. The researchers focused on this CGG repeat because it is associated with hereditary neurological disorders such as fragile X syndrome and FRAXE mental impairment.

In a study to be published in the January 2009 issue of the journal Nature Structural and Molecular Biology, Sergei Mirkin, White Family Professor of Biology at Tufts' School of Arts and Sciences, along with graduate students Irina Voineagu and Christine F. Surka and postdoctoral fellows Alexander A. Shishkin and Maria M. Krasilnikova, explored the link between CGG repeats and replication delays. Mirkin's research was funded by the National Institutes of Health.

Effect of palindromes

Past research from Mirkin's lab had shown that peculiar long DNA sequences named palindromes change the shape of the molecule from a double helix into a hairpin-like structure and, as a result, stall replication. When this happens chromosomes can break during cell division.

For the new research, Mirkin and his team analyzed different cloned CGG repeats in a mammalian cell culture line called COS-1 and in budding yeast cells. The researchers found that short triplets do not cause any problems. When the repeats got longer, however, the replication machinery got jammed and stalled in both systems. Thus, replication stalling likely accounts for the chromosomal fragility. They believe that this stalling is due to the formation of a stable, hairpin-like DNA structure formed by long CGG repeats.

Abnormal structures disable cellular checkpoints

"Our cells have evolved elaborate 'checkpoint' mechanisms to detect replication blocks and trigger the instant 'restart' of DNA replication there," said Mirkin. "Are the CGG repeats causing the checkpoints to fail?"

With replication stalled, Mirkin and his research team found that the CGG repeats did not respond to the key checkpoint protein called Mrc1 in yeast or claspin in humans. Both proteins work to repair replication malfunctions during the S phase of the cell cycle. Apparently, the unusual structure of CGG repeats acts to escape the cellular checkpoints. As a consequence, chromosomes under-replicate, become fragile and break.

Source : Tufts University


Алкоголь - не всегда яд.

Алкоголь может обладать цитопротекторными свойствами. Читаю на http://scienceblogs.com/corpuscallosum/2008/12/possible_cytoprotective_effect.php:

Possible Cytoprotective Effect of Alcohol

Category: Medicine • Neuroscience
Posted on: December 31, 2008 9:03 AM, by Joseph j7uy5
Ethanol is a poison. But the difference between poison and medicine sometimes is only a matter of dosage.

For decades, there have been studies that purport to show a small benefit from regular consumption of small amounts of ethanol, with obvious problems caused by excessive alcohol consumption. Physicians, however, are divided about what to do with this information. Do we recommend that people have one alcohol beverage per day, or do we remain silent on the subject?

One reason to be reluctant to recommend moderate drinking, as opposed to abstinence, is that it is very difficult to prove that such recommendations would help anyone. It is one thing to show an association between moderate drinking and improved health; however, that does not mean that teetotalers who start drinking moderately will experience any benefit at all, much less have the population experience more benefit than harm.

There is another reason to be hesitant about making such a recommendation. That is, we do not know how the intervention would work, on a molecular level. Although it is not strictly necessary that we know the mechanism of action, it would help us feel more comfortable that the recommendation makes sense.

So now we have evidence that gives an inkling of what the mechanism might be, with regard to protection against dementia and heart disease:

Alcohol in Moderation, Cardioprotection, and Neuroprotection: Epidemiological Considerations and Mechanistic Studies
Collins M, et al "Alcohol in moderation, cardioprotection, and neuroprotection: epidemiological considerations and mechanistic studies" Alcoholism: Clinical and Experimental Research 2008; DOI: 10.1111/j.1530-0277.2008.00828.x

In contrast to many years of important research and clinical attention to the pathological effects of alcohol (ethanol) abuse, the past several decades have seen the publication of a number of peer-reviewed studies indicating the beneficial effects of light-moderate, nonbinge consumption of varied alcoholic beverages, as well as experimental demonstrations that moderate alcohol exposure can initiate typically cytoprotective mechanisms. A considerable body of epidemiology associates moderate alcohol consumption with significantly reduced risks of coronary heart disease and, albeit currently a less robust relationship, cerebrovascular (ischemic) stroke. Experimental studies with experimental rodent models and cultures (cardiac myocytes, endothelial cells) indicate that moderate alcohol exposure can promote anti-inflammatory processes involving adenosine receptors, protein kinase C (PKC), nitric oxide synthase, heat shock proteins, and others which could underlie cardioprotection. Also, brain functional comparisons between older moderate alcohol consumers and nondrinkers have received more recent epidemiological study. In over half of nearly 45 reports since the early 1990s, significantly reduced risks of cognitive loss or dementia in moderate, nonbinge consumers of alcohol (wine, beer, liquor) have been observed, whereas increased risk has been seen only in a few studies. Physiological explanations for the apparent CNS benefits of moderate consumption have invoked alcohol's cardiovascular and/or hematological effects, but there is also experimental evidence that moderate alcohol levels can exert direct "neuroprotective" actions—pertinent are several studies in vivo and rat brain organotypic cultures, in which antecedent or preconditioning exposure to moderate alcohol neuroprotects against ischemia, endotoxin, β-amyloid, a toxic protein intimately associated with Alzheimer's, or gp120, the neuroinflammatory HIV-1 envelope protein. The alcohol-dependent neuroprotected state appears linked to activation of signal transduction processes potentially involving reactive oxygen species, several key protein kinases, and increased heat shock proteins. Thus to a certain extent, moderate alcohol exposure appears to trigger analogous mild stress-associated, anti-inflammatory mechanisms in the heart, vasculature, and brain that tend to promote cellular survival pathways. [emphasis added]

Note that the paper does not present original research findings. Rather, the authors describe the results of a literature review and roundtable discussion.

It is important to recognize several caveats in the interpretation of this paper. For one, much of the research they reviewed was done in animals other than humans. Also, there are many different kinds of alcohol beverages. Some but not all contain biologically active components, such as resveratrol, that introduce confounding variables.

Importantly, the authors note that not all studies found benefit. More than half of the epidemiological studies did suggest benefit, but a few indicated potential harm.

All the work regarding the molecular mechanisms is interesting. Perhaps some day will will learn enough to be able to produce a pharmaceutical product that provides just as much benefit as a glass of wine per day, at a cost that is merely six times greater than the cost of the natural product. And perhaps it will get rid of the known risks, instead presenting us with the potential for new, unknown risks.


Контроль повреждаемости ДНК

Ещё одна статья, о моих любимых повреждениях ДНК. Здесь особенно подчёркивается роль протеин-киназ: http://www.eurekalert.org/pub_releases/2009-01/bi-bri010509.php

Public release date: 5-Jan-2009
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Contact: Josh Baxt
Burnham Institute
Burnham researchers illuminate mechanisms that regulate DNA damage control and replication

LA JOLLA, Calif., January 5, 2008—Scientists at Burnham Institute for Medical Research (Burnham) have demonstrated important new roles for the protein kinase complex Cdc7/Dbf4 or Cdc7/Drf1 (Ddk) in monitoring damage control during DNA replication and reinitiating replication following DNA repair. Since Ddk is often deregulated in human cancers, this new understanding of its role in DNA damage control could help shape new cancer therapies. The research was published in the December 24 issue of Molecular Cell.

Accurate DNA replication is essential for maintaining the stability of the genome. When errors occur, replication halts through a quality control process called the S-phase checkpoint. Replication is only restarted after the errors have been repaired. One of several proteins required for DNA replication, Ddk has long been thought to play an important role in the S-phase checkpoint, despite the lack of definitive evidence. In this study, Burnham researchers show that Ddk actively controls S-phase checkpoint signaling and plays a crucial role in triggering the re-initiation of DNA replication once damage has been repaired.

"This protein kinase complex is not only monitoring DNA replication, it's also monitoring the S-phase checkpoint," says Wei Jiang, Ph.D., the study's principal investigator. "If replication is accurate, then Ddk allows DNA synthesis to continue normally. If there is DNA damage, replication is halted at this checkpoint. The most important thing is to stop replication in order to allow for DNA repair and to avoid catastrophe for the cell. Our study demonstrates that Ddk not only activates the initiation of DNA replication, but it also monitors the checkpoint during DNA damage control and eventually overrides the checkpoint to re-initiates DNA replication."

These findings suggest a highly complex role for Ddk in DNA replication, S-phase checkpoint monitoring and DNA replication re-initiation after repair. The roles of Ddk in controlling the DNA replication machinery for genome stability and fidelity may make it an excellent target for the development of new cancer treatments.


This study, performed by Toshiya Tsuji, Ph.D. and Eric Lau, Ph.D. from the Jiang laboratory in collaboration with Gary Chiang, Ph.D., was funded by a grant from the National Institutes of Health.

About Burnham Institute for Medical Research

Burnham Institute for Medical Research is dedicated to revealing the fundamental molecular causes of disease and devising the innovative therapies of tomorrow. Burnham, with operations in California and Florida, is one of the fastest growing research institutes in the country. The Institute ranks among the top four institutions nationally for NIH grant funding and among the top 25 organizations worldwide for its research impact. Burnham utilizes a unique, collaborative approach to medical research and has established major research programs in cancer, neurodegeneration, diabetes, infectious and inflammatory and childhood diseases. The Institute is known for its world-class capabilities in stem cell research and drug discovery technologies. Burnham is a nonprofit, public benefit corporation. For more information, please visit www.burnham.org.