Researchers discover method to unravel malaria's genetic secrets

"The malarial genome has been a black box. Our technique allows us to open that box, so that we can learn what genes in the most lethal human parasite actually do," said Dennis Voelker, PhD, Professor of Medicine at National Jewish Health and senior author on the paper that appeared in the January 2, 2012 , issue of the Journal of Biological Chemistry. "This could prove tremendously valuable in the fight against a disease that has become increasingly drug-resistant."

The genome of P. falciparum was sequenced in 2002, but the actual functions of many of the organism's genes have remained elusive. One of the primary methods for discovering gene function is to copy a specific gene, insert it into a model organism that is easy to grow, often the yeast Saccharomyces cerevisiae, then draw on the incredible knowledge base about yeast and its abundant genetic variants to discover how that inserted gene changes the organism's biology.

DNA is composed of building blocks with the shorthand designations A,T,C and G. The genome of P. falciparum is odd because it is particularly rich in A's and T's. Because of this A-T-rich nature, P. falciparum genes generally do not function when they are inserted into other organisms. As a result, scientists have been largely stymied when trying to understand the functions of P. falciparum's genes.

It turns out, however, that P. falciparum has a close cousin, P. knowlesi, which shares almost all its genes with P. falciparum, but with fewer A's and T's. As a result, P. knowlesi genes function well when inserted into yeast. Scientists can now insert P. knowlesi genes into yeast, discover their function, and then match them to corresponding genes in P. falciparum, which reveals the function of the malarial parasite's genes.

"This technique could lead to an explosion in knowledge about malaria and the parasite that causes it." said Dr. Voelker.

The researchers used the technique to discover a new gene involved in the synthesis of lipids in cell membranes of P. falciparum. The gene, phosphatidylserine decarboxylase, directs the formation of a protein unique to malarial parasites and is a potential therapeutic target. For example, selective disruption of lipid synthesis in P. falciparum, would prevent the organism from making new cell membranes, growing and reproducing in human hosts.

Provided by National Jewish Health

Researchers unravel biochemical factor important in tumor metastasis

According to study corresponding author Shengyu Yang, Ph.D., of Moffitt's Comprehensive Melanoma Research Center and the Department of Tumor Biology, elevated Transforming Growth Factor beta in the tumor microenvironment may be responsible for fascin over-expression, which in turn can promote metastasis in some metastatic tumors.

TGF beta is a versatile cytokine involved in many physiological and pathological processes in adults and in the developing embryo, including cell growth, cell differentiation, cell death (apoptosis) and cellular homeostasis. TGF beta is best known as a tumor suppressor, exerting growth inhibitory roles in normal tissue and early stage tumors. However, many metastatic tumors are able to overcome the growth inhibition and secreted elevated levels of TGF beta to promote tumor metastasis. How TGF beta promotes metastasis is not completely understood. The authors suggested that fascin may be the key to understand the pro-metastasis function of TGF beta, as fascin knockdown almost completely abolished TGF beta induced tumor cell migration and invasion.

The researchers explained that fascin levels are low or not detected in normal tissues, but are highly elevated in malignant tumors. Also, high fascin expression is associated with poor prognosis. It has been clear for some time, they noted, that there is a causal role for fascin over-expression in tumor cell dissemination. However, the underlying mechanism for the elevation of fascin levels has not been clarified. Their analysis using cell culture- based assay and patient microarray data mining strongly suggests that elevated TGF beta levels in tumors lead to fascin overexpression, which in turn promotes metastasis.

"Our data suggests that fascin is an immediate TGF beta target gene essential for its pro-invasion activity in cancer metastasis," explained Yang.

While there have been many studies on the role of fascin in tumor cell migration and metastasis, the current study is first to report that TGF beta elevates fascin protein expression to promote invasion, particularly in tumor cells of spindle-shaped – the kind of morphology associated with high tumor invasiveness and more metastatic disease.

"The finding that TGF beta only induces fascin over-expression in highly metastatic tumor cells is especially interesting," said Yang. "Therapies targeting fascin may block TGF beta mediated metastasis without interfering with the tumor suppressor role of TGF beta in normal tissues."

Provided by H. Lee Moffitt Cancer Center & Research Institute

What's the label? Helping to unravel the role of nature in biosynthetic pathways

Terpenoids are a very large and diverse class of compounds which includes certain hormones, flavors, and drugs, such as steroids, cinnamon or menthol, and antibacterials. They are found in all living organisms, but their biosynthesis is not yet fully understood. To learn more about how plants or animals make these important natural products, chemists typically turn to labeling experiments.

In these experiments, synthetic compounds are used that carry a tag or isotopic label, that is, heavy versions of atoms are chemically introduced into the precursors of biomolecules. These marked precursors are then fed to organisms. Just where these tags appear in natural terpenoids tells researchers more about how the organism made the compounds. Mevalonolactone (MVA) is an important precursor for terpenoids, and Jeroen S. Dickschat and a team of scientists from Braunschweig (Germany) have now prepared a series of labeled MVA derivatives that will help to unravel the biosynthesis of terpenoids, as they report in the European Journal of Organic Chemistry.

Chemists are able to follow the incorporation of isotopic labels into natural products by standard analytical methods. This is one of the most basic approaches used to determine biosynthetic pathways, as the method is only limited by the availability of the labeled compounds. Deuterated derivatives carrying a heavy version of hydrogen are a good choice for the study of terpenoids, as several steps in their biosynthesis can include rearrangements of hydrogen atoms. Deuterated MVAs have been used in the past to unravel the assembly of terpenoids; however, their availability is limited. The synthesis of such materials can be highly complex and laborious, and the isotopically labeled starting materials or reagents can be expensive. Therefore, short, efficient, and flexible routes that allow isotopic labeling at specific locations are required.

Thus, the authors set out to develop a synthetic route to deuterated MVA derivatives that allows for the independent introduction of deuterium into any position or into any combination of different positions using low-cost deuterated reagents. The team demonstrated that MVA could be labeled by using classical organic chemistry transformations, and importantly, the introduction of deuterium at any carbon atom in MVA was possible. The applicability of their route was demonstrated in the synthesis of five exemplary MVA derivatives with deuterium incorporation at different and specific locations. With the possibility to prepare new labeled MVA derivatives, scientists will now be able to address several important questions in the biosynthetic investigations of terpenoids.

More information: Jeroen S. Dickschat, Synthesis of Deuterated Mevalonolactone Isotopomers, European Journal of Organic Chemistry, Permalink to the article: http://dx.doi.org/ … oc.201100188

Provided by Wiley (news : web)