(Press-News.org) Evolutionary theory says mutations are blind and occur randomly. But in the phenomenon of adaptive mutation, cells can peek under the blindfold, increasing their mutation rate in response to stress.
Scientists at Winship Cancer Institute, Emory University have observed that an apparent "back channel" for genetic information called retromutagenesis can encourage adaptive mutation to take place in bacteria.
The results are scheduled for publication in PLOS Genetics on Tuesday, August 25.
"This mechanism may explain how bacteria develop resistance to some types of antibiotics under selective pressure, as well as how mutations in cancer cells enable their growth or resistance to chemotherapy drugs," says senior author Paul Doetsch, PhD.
Doetsch is professor of biochemistry, radiation oncology and hematology and medical oncology at Emory University School of Medicine and associate director of basic research at Winship Cancer Institute. The first author of the paper is recently graduated Genetics and Molecular Biology graduate student Jordan Morreal, PhD.
Retromutagenesis resolves the puzzle: if cells aren't growing because they're under stress, which means their DNA isn't being copied, how do the new mutants appear?
The answer: a mutation appears in the RNA first.
The mutation in the RNA results in a protein with augmented function that helps the cells grow, giving them a chance to replicate their DNA and for subsequent DNA mutations to exert their effects.
In the PLOS Genetics paper, scientists led by Doetsch and colleague Bernard Weiss, MD, provide evidence that retromutagenesis is occurring in E. coli bacteria forced to grow on the sugar lactose as their only source of energy.
The bacterial strain tested had a disabling mutation in a gene that, if functional, would allow the cells to use lactose. When exposed to high levels of nitrous acid, a DNA-damaging agent, mutations appeared in the bacteria and some of the bacteria could grow. By analyzing where exactly on the DNA the mutations occurred, the scientists concluded that retromutagenesis was contributing to bacterial growth.
"Most of the previous experiments on adaptive mutation have attempted to rule out growth of the parent cells during selection, which is almost impossible to do with the necessary rigor... Instead of measuring overall DNA replication via cellular growth in the parental population during selection as in previously published experiments, we are able to gauge DNA replication specifically in the revertants via NTS [non-transcribed strand] mutations. Low frequency of NTS mutations found after direct selection indicates there was little DNA synthesis before gene expression and strongly supports the model of retromutagenesis," the authors write.
The authors note that retromutagenesis may explain previous observations of bacteria developing resistance to the antibiotic ciprofloxacin, as well as mutations in the human p53 Ras oncogene, seen in many forms of cancer.
INFORMATION:
The research was supported by the National Institute of Environmental Health Sciences (P01ES011163).
Tropical Cyclone Atsani appeared to look more like a frontal system in infrared imagery from NASA's Aqua satellite.Early on August 26, the Joint Typhoon Warning Center issued their final bulletin on the system as it was transitioning into an extra-tropical cyclone,
The Atmospheric Infrared Sounder or AIRS instrument that also flies aboard Aqua captured infrared data on the storm on August 25 at 14:47 UTC (10:47 a.m. EDT). Cloud top temperatures in thunderstorms northeast of the center were colder than -63F/-52C, indicating high, strong thunderstorms with the potential ...
Bats are natural reservoirs of several important emerging viruses, and because cross-species transmission appears to be quite common among bats, it's important to study bats in a community context rather than concentrating on individual species.
Researchers have now used such an approach to identify characteristics of cross-species virus transmission in bats and rodents, another important viral host. The investigators uncovered evidence to suggest that viruses pass more easily between bat species than between rodent species, and they found that characteristics unique ...
In a new review of all relevant medical research on breastfeeding practices, infants 0 to 5 months of age who were predominantly, partially, or not breastfed had 1.5-, 4.8-, and 14.4-times higher risks of dying, respectively, compared with exclusively breastfed infants. Also, children aged 6 to 23 months who were not breastfed had about a 2-times higher risk of dying than children who were continued on breastfeeding.
"The findings underscore the importance of optimal breastfeeding practices during infancy and early childhood," said Dr. M. Jeeva Sankar, lead author of ...
(Boston)--Twenty-five percent of men currently taking Finasteride or Dutasteride, popularly known as Proscar and Avodart, for the treatment of benign prostate enlargement (BPH), appear not to benefit from taking these medications. Those prescribed Propecia or Avodart for male pattern hair loss (known as alopecia) are also at risk for adverse events elicited by these drugs.
These findings are part of an international, collaborative review currently online in the journal Endocrine Reviews and Metabolic Disorders. Led by Abdulmaged Traish, PhD, professor of biochemistry ...
In early August, biologist Peter Ward returned from the South Pacific with news that he encountered an old friend, one he hadn't seen in over three decades. The University of Washington professor had seen what he considers one of the world's rarest animals, a remote encounter that may become even more infrequent if illegal fishing practices continue.
The creature in question is Allonautilus scrobiculatus, a species of nautilus that Ward and a colleague had previously discovered off of Ndrova Island in Papua New Guinea. Nautiluses are small, distant cousins of squid and ...
RIVERSIDE, Calif. - Barley, a widely grown cereal grain commonly used to make beer and other alcoholic beverages, possesses a large and highly repetitive genome that is difficult to fully sequence. Now a team led by scientists at the University of California, Riverside has reached a new milestone in its work, begun in 2000, on sequencing the barley genome. The researchers have sequenced large portions of the genome that together contain nearly two-thirds of all barley genes.
The new information, published in The Plant Journal, will not only expand geneticists' knowledge ...
A recent randomized trial conducted by researchers at Abbott Northwestern Hospital, part of Allina Health, found that inpatient palliative care (PC) visits were associated with improved quality of life and symptom burden for patients with heart failure (HF).
Because of these results, Abbott Northwestern conducted a new study, "A Description of Inpatient Palliative Care Actions for Patients with Acute Heart Failure," published June 30 by the American Journal of Hospice and Palliative Medicine. The study aimed to identify and describe what actions PC providers took to ...
BOSTON - A new study led by researchers at Boston Medical Center (BMC) indicates that variations in opioid receptor genes are associated with more severe neonatal abstinence syndrome (NAS) in newborn babies. The findings, published online in Drug & Alcohol Dependence, could help lead to the development of individualized treatment plans tailored to each infants' risk of requiring medication to curb their NAS symptoms, which could help improve these patients' outcomes and reduce how long some stay in the hospital.
NAS is present in newborn babies who have been exposed ...
Jaclyn Tabor and Jessica Calarco tap a novel data source to track changing attitudes toward parenting during the 20th and early 21st centuries: cartoons in the New Yorker magazine.
"We find that portrayals of children and child-rearing are both more varied and more fluctuating than existing research would suggest," said Tabor, an Indiana University Bloomington doctoral student in sociology. "Contemporary cartoons celebrate children but also recognize the significant challenges children create for parents. Cartoons from the 1920s and 1930s -- when rates of childlessness ...
Less than a month before Congress votes on whether to reauthorize a controversial program mandating healthier school lunches, a new study confirms the suspicions of school officials - many students are putting the fruits and vegetables they're now required to take straight into the trash, consuming fewer than they did before the law took effect.
The new study, published online in Public Health Reports on Aug. 25, is the first to use digital imaging to capture students' lunch trays before and after they exited the lunch line.
It is also one of the first to compare fruit ...
