Friday, April 30, 2010

A Second Level of Gene Transcription Control

Controlling gene expression is an important key to controlling ageing, cancer, diseases of degeneration and autoimmunity, and virtually any other mechanism of human health and pathology. As scientist learn more about the mechanisms of gene expression, they also discover new ways of intervening to prevent or treat disease. The following article discusses the ongoing clarification of an important added complexity of gene expression that will certainly be exploited for good effect before long.
A new study published online today (April 29) in Cell helps drive home just how widespread this second level of gene control is, and implicates a cancer-causing transcription factor as a major player in the process.

"This is another piece in the puzzle that demonstrates controlling the elongation phase of transcription" -- the production of messenger RNA as the transcriptional apparatus propagates down the gene -- "is one of the more important control mechanisms," said biochemist David Price of the University of Iowa, who was not involved in the study. "[This] paper is going to help convince the field that this is just the way it is."

Scientists once believed that transcription factors promoted gene expression simply by recruiting RNA polymerase II (Pol II) machinery to the promoter region of their target genes, and letting the Pol II take over from there. But over the last 20 years, several lines of evidence indicated that once bound to the promoter, Pol II pauses, or stalls, just a little ways down the transcript, and needs another signal (such as a transcription factor) to continue transcribing the gene. Recent evidence suggests that this pause is a widespread phenomenon in the genome, but "there's been some reluctance in the transcription community to accept that there are these polymerases poised [just past the start site] all throughout the human genome," Price said.

Exploring the role of this mechanism of gene control in mouse embryonic stem cells (ESCs), molecular biologist Richard Young of the Whitehead Institute for Biomedical Research and Massachusetts Institute of Technology and his colleagues have all but eliminated that doubt. They found evidence of paused polymerases on the vast majority of genes -- both those actively being transcribed and those that remained silent.

"We're thinking now that at all genes where RNA polymerase II initiates transcription, there is a pause step," Young said. "So even genes that are being currently and actively transcribed, polymerase initiates [transcription], but must go through this pause checkpoint before it's allowed to proceed to elongation."

The team further showed that the well-studied transcription factor c-Myc, which is involved in cell self-renewal and proliferation and has been implicated in 15-30 percent of human cancers, is an example of the additional factor needed to push Pol II past the pause. Instead of promoting gene expression by recruiting Pol II to the genes, c-Myc appears to release already-initiated polymerases from this paused stage. It does so by recruiting a protein known as positive transcription elongation factor b (P-TEPb) to release the Pol II to finish what it started.

Understanding the details of this mechanism of gene control could thus have important implications for the treatment of a variety of ailments, said molecular biologist and clinician B. Matija Peterlin of the University of California, San Francisco, who also did not participate in the research. "I think it brings a whole new aspect to not just cancer [research] but" other diseases as well, Peterlin said. "If you attenuate the activity of P-TEFb, you might be able to [develop] a non-gene-modifying way treat a lot of human diseases."

P.B. Rahl, et al., "c-Myc regulates transcriptional pause release," Cell:141,1-14,2010.

Read more: More support for transcription trick - The Scientist - Magazine of the Life Sciences _the-scientist


Friday, April 09, 2010

Nano-Magnets Lead Stem Cells to Damaged Heart

A promising way of healing damaged heart tissue involves combining stem cells with nano-magnets.  The magnetised stem cells are then steered to the site of damage, using magnetic fields.
"Stem cell therapies show great promise as a treatment for heart injuries, but 24 hours after infusion, we found that less than 10 percent of the stem cells remain in the injured area," said Eduardo Marbán, M.D., director of the Cedars-Sinai Heart Institute. "Once injected into a patient's artery, many stem cells are lost due to the combination of tissue blood flow, which can wash out stem cells, and cardiac contraction, which can squeeze out stem cells. We needed to find a way to guide more of the cells directly to the area of the heart that we want to heal."
Marbán's team, including Ke Cheng, Ph.D. and other researchers, then began a new animal investigation, loading cardiac stem cells with micro-size iron particles. The iron-loaded cells were then injected into rats with a heart attack. When a toy magnet was placed externally above the heart and close to the damaged heart muscle, the stem cells clustered at the site of injury, retention of cells in the heart tripled, and the injected cells went on to heal the heart more effectively.
"Tissue viability is enhanced and heart function is greater with magnetic targeting," said Marbán, who holds the Mark Siegel Family Foundation Chair at the Cedars-Sinai Heart Institute and directs Cedars-Sinai's Board of Governors Heart Stem Cell Center. "This remarkably simple method could easily be coupled with current stem cell treatments to enhance their effectiveness." _Physorg
Image Source

The combination of stem cells with nanotechnology provides another synergistic surprise, loaded with hope for future cures and life extension potential.

Tomorrow's medical treatments will be more individualised, more targeted to specific systems and tissues. As a result, the collateral damage will be lessened, interventional dosing and exposure can be moderated, and a desired outcome can be made more likely.

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Thursday, April 08, 2010

Switching Off Cancer Using Nanoparticles


Scientists at Cal Tech in Pasadena have used targeted nanoparticles to alter the gene expression of cancer cells in human cancer patients. Their phase 1 clinical trial established the efficacy of their targeting approach and was published in the 21 March advanced online Nature.
Lead author Dr Mark E Davis, the Warren and Katharine Schlinger Professor of Chemical Engineering at Caltech, told the press that in principle:

"Every protein now is druggable because its inhibition is accomplished by destroying the mRNA."

"And we can go after mRNAs in a very designed way, given all the genomic data that are and will become available," he added.

However, as is often the case, what looks straightforward in theory is fraught with obstacles when you try and apply it in practice. One such difficulty, when trying to apply RNAi technology to humans is, how do you deliver such tiny, fragile molecules, the small interfering RNAs (siRNAs), to the tumors?

Senior author Dr Antoni Ribas, an associate professor of medicine and surgery and a researcher at UCLA's Jonsson Comprehensive Cancer Center, said:

"There are many cancer targets that can be efficiently blocked in the laboratory using siRNA, but blocking them in the clinic has been elusive."

Davis and colleagues had a solution: they had already been working on ways to deliver nucleic acids into cells before RNAi was discovered. They eventually came up with a method featuring four components, one of which is a unique polymer that can assemble itself into a targeted nanoparticle that carries siRNA.

Davis explained that their nanoparticles can take the siRNAs into the targeted site within the body, and when they reach their target, the cancer cells inside the tumor, the nanoparticles enter the cells and release the siRNAs.

The researchers used a new method developed at Caltech to find and image the nanoparticles inside cells biopsied from the tumors of several patients taking part in the trial.

They also found that the more nanoparticles a patient was given, the more were present in the tumor cells: thus establishing there was a dose-dependent response.

But what was even better, said Davis, was they found evidence the siRNAs had done their job: in the cells they analyzed, which had been targeted to prevent production of the cell-growth protein ribonucleotide reductase, they found the corresponding mRNA had been degraded. Thus effectively the siRNAs had silenced the gene that was fuelling cancer growth.

Davis explained that this was the first time that anyone has found an RNA fragment from patient cells showing that the RNAi mechanism had severed the mRNA at exactly the correct base:

"It proves that the RNA interference mechanism can happen using siRNA in a human," said Davis.

Ribas said:

"This research provides the first evidence that what works in the lab could help patients in the future by the specific delivery of siRNA using targeted nanoparticles."

"We can start thinking about targeting the untargetable," he added. _MedicalNews

As the authors say, this is just the beginning. Silencing gene expression by targeting the mRNA is only a temporary approach. If such treatment kills all of the cancer cells -- and leaves normal cells alone -- then being only temporary will not be an impediment.

But in many types of cancer -- and other disease -- it will not be enough merely to block the offensive mRNA. You will want to alter the DNA itself to put a permanent stop to the flow of a particular unwanted mRNA. That will require a different approach altogether.

The challenge is vast and seemingly unending. But it is worthwhile.

H/T Cuanas

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New Hope for Treating Autoimmune Diseases


The autoimmune diseases cause untold pain, misery, and hardship -- not to mention expense -- throughout the human lifespan. When the person's immune system attacks other cells in his own body, treatment options are generally limited and sub-optimal. But now, researchers at the University of Alberta, Calgary, have devised a treatment (and prevention) for Type 1 diabetes which may lead to a revolution in the treatment and prevention of autoimmune diseases -- such as multiple sclerosis, rheumatoid arthritis, lupus, and many more.
Researchers from the University of Calgary in Alberta, led by Dr. Pere Santamaria, were looking to halt the autoimmune response that causes type 1 diabetes, but do so without damaging the immune cells that control and regulate the immune system or that protect against infections. So the team focused on developing a highly targeted antigen-specific immunotherapy - one, they explained, that could address the "internal tug-of-war between aggressive T cells that want to cause the disease and weaker T cells that want to stop it from occurring."

The researchers produced a unique vaccine comprising nanoparticles, which are thousands of times smaller than the size of a cell. They coated the particles with type 1 diabetes-relevant peptides, or protein fragments, that were bound to certain molecules that play a critical role in immune cell communication (called MHC molecules).

In the mice, the nanoparticle treatment expanded a type of regulatory T cell -- these cells ultimately suppressed the aggressive immune attack that destroys the insulin-producing beta cells of the pancreas. The researchers noted that the expanded cells shut down the immune attack by preventing autoreactive immune cells from being stimulated, either by the peptide contained in the vaccine or by any other diabetes autoantigen presented simultaneously by antigen-presenting cells. With the immune response that causes diabetes blocked, mice with type 1 diabetes regained normal blood sugars. And those that would have contracted the disease didn't.

The study also provides important - and promising - insight into the ability to translate these findings into therapeutics for people: Nanoparticles that were coated with molecules specific to human type 1 diabetes were able to restore normal blood sugar levels in a humanized mouse model of diabetes (that is, a mouse that has been genetically altered to biologically simulate type 1 diabetes in people). _ jdrf

Article abstract from Cell

H/T Brian Wang

Science is slowly but surely decoding the complex signaling involved in life, disease, and ageing. With the better tools being provided by advanced genetics, nanotechnology, immunology, and information technology, it is easy to feel that there are no secrets of life that will not be unwrapped and decoded sooner or later.


Wednesday, April 07, 2010

Human Cell Aging Reversed by Biotime

Biotime researchers report the successful resetting of the "age clock" of mature human cells back to the embryonic age. This was apparently accomplished using telomeric technology similar to what Geron has been working on.
In the article, BioTime and its collaborators demonstrate the successful reversal of the developmental aging of normal human cells. Using precise genetic modifications, normal human cells were induced to reverse both the "clock" of differentiation (the process by which an embryonic stem cell becomes the many specialized differentiated cell types of the body), and the "clock" of cellular aging (telomere length). As a result, aged differentiated cells became young stem cells capable of regeneration.

More links, videos, and information from Brian Wang and at the BioTime website.

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