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Renegade RNA — Clues to cancer and normal growth
January 05, 2007Researchers at Johns Hopkins have discovered that a tiny piece of genetic code apparently goes where no bit of it has gone before, and it gets there under its own internal code.
A report on the renegade ribonucleic acid, and the code that directs its movement, will be published Jan. 5 in Science.
That's why normally microRNAs always have appeared to stick close to the cell's protein-making machinery.
But during a survey of more than 200 of the 500 known microRNAs found in human cells, Mendell's team discovered one lone microRNA "miles away" -- in cellular terms -- from all the others.
"It was so clearly in the wrong place at the wrong time for what we thought it was supposed to be doing that we just had to figure out why," says Hun-Way Hwang, a graduate student in human genetics and contributor to the study.
Consisting of only 20 to 25 nucleotide building blocks (compared to other types of RNA that can be thousands of nucleotides long), each microRNA has a different combination of blocks. Mendell's team realized that six building blocks at the end of the wayward miR-29b microRNA were noticeably different from the ends of other microRNAs.
Suspicious that the six-block end might have something to do with miR-29b's location, the researchers chopped them off and stuck them on the end of another microRNA. When put into cells, the new microRNA behaved just like miR-29b, wandering far away from the cell's protein-making machinery and into the nucleus, where the cell's genetic material is kept.
The researchers then stuck the same six-block end onto another type of small RNA, a small-interfering RNA or siRNA that turns off genes. This also forced the siRNA into the nucleus.
According to Mendell, these results demonstrate for the first time that despite their tiny size, microRNAs contain elements consisting of short stretches of nucleotide building blocks that can control their behavior in a cell. Mendell hopes to take advantage of the built-in "cellular zip code" discovered in miR-29b as an experimental tool. For example, he plans to force other microRNAs and siRNAs into the nucleus to turn off specific sets of genes.
Mendell's team is actively hunting for additional hidden microRNA elements that control other aspects of their behavior in cells. They also are curious to figure out what miR-29b is doing in the nucleus. Because microRNAs have been implicated in cancer as well as normal development, Mendell hopes that further study of miR-29b will reveal other, hidden functions of microRNAs.
Johns Hopkins Medical Institutions
Microrna Current Events and Microrna News RSSResearchers discover brain tumor's 'grow-or-go' switch
Cancer cells in rapidly growing brain tumors must adjust to periods of low energy or die. When energy levels are high, tumor cells grow and proliferate. When levels are low, the cells grow less and migrate more.
Study identifies key cause of chronic leukemia progression
Researchers have discovered a key reason why a form of leukemia progresses from its more-treatable chronic phase to a life-threatening phase called blast crisis.
Key player found for a cancer typical in Down syndrome
Between 5 and 10 percent of babies with Down syndrome develop a transient form of leukemia that usually resolves on its own.
Penn Biologists Determine MicroRNA Activity Is Suppressed in Mouse Ovum
Biologists at the University of Pennsylvania studying oocytes in mice, the immature egg cells necessary for sexual reproduction, have demonstrated an unusual behavior in microRNA, or miRNA, activity that may be the first event in reprogramming the differentiated oocyte into pluripotent blastomeres of the embryo.
MicroRNA: a glimpse into the past
The last ancestor we shared with worms, which roamed the seas around 600 million years ago, may already have had a sophisticated brain that released hormones into the blood and was connected to various sensory organs.
Tiny RNA has big impact on lung cancer tumors
Researchers from Yale University and Mirna Therapeutics, Inc., reversed the growth of lung tumors in mice using a naturally occurring tumor suppressor microRNA.
Experimental agent reduces breast cancer metastasis to bone
Researchers have reduced breast cancer metastasis to bone using an experimental agent to inhibit ROCK, a protein that was found to be over-expressed in metastatic breast cancer.
Study sheds light on evolution of human complexity
A painstaking analysis of thousands of genes and the proteins they encode shows that human beings are biologically complex, at least in part, because of the way humans evolved to cope with redundancies arising from duplicate genes.
MicroRNA-mediated metastasis suppression
Metastases are responsible for over 90% of cancer deaths. In the upcoming issue of G&D, Dr. Robert Weinberg (MIT) and colleagues lend molecular insight into how microRNAs suppress tumor metastasis.
Texas A&M researchers find new mechanism for circadian rhythm
Molecules that may hold the key to new ways to fight cancer and other diseases have been found to play an important role in regulating circadian rhythm, says Liheng Shi, a researcher in Texas A&M's Department of Veterinary Integrative Biosciences.
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