RNA molecules, made from DNA, are best known for their role in protein production. MicroRNAs (miRNAs), however, are short (~22) nucleotide RNA sequences found in plants and animals that do not encode proteins but act in gene regulation and, in the process, impact almost all biological processes — from development to physiology to stress response.
Against a backdrop of a digital rendition of the endoplasmic reticulum, the image depicts a wild-type Arabidopsis plant (center) surrounded by mutants that are compromised in the translation inhibition activity of plant microRNAs. The developmental defects of the mutants highlight the important contribution of the translation inhibition activity of plant microRNAs to developmental patterning.
Credit: X. Chen Lab, UC Riverside.
Present in almost in every cell, microRNAs are known to target tens to hundreds of genes each and to be able to repress, or "silence," their expression. What is less well understood is how exactly miRNAs repress target gene expression.
Now a team of scientists led by geneticists at the University of California, Riverside has conducted a study on plants (Arabidopsis) that shows that the site of action of the repression of target gene expression occurs on the endoplasmic reticulum (ER), a cellular organelle that is an interconnected network of membranes — essentially, flattened sacs and branching tubules — that extends like a flat balloon throughout the cytoplasm in plant and animal cells.
Research on miRNAs has increased tremendously since they were first identified about 20 years ago. In the case of diseases, if some genes are up- or down-regulated, miRNAs can be used to change the expression of these genes to fight the diseases, thus showing therapeutic potential.
MicroRNAs are known to regulate target genes by two major modes of action: they either destabilize the target RNAs, leading to their degradation, or they do not impact the stability of the target RNAs, but simply prevent them from being translated into proteins — a process known as translation inhibition. The end result of translation inhibition is that the genes do not get expressed. Just how miRNAs cause translational inhibition of their target genes is not well understood.
"We were surprised that the ER is required for the translational inhibition activity of miRNAs," Chen said. "This new knowledge will expedite our understanding of the mechanism of gene silencing. Basically, now we know where to look: the ER. We also suspect it is the rough ER portions that are involved."
Chen explained that the ER has two types: rough and smooth. Rough ER, which synthesizes and packages proteins, looks bumpy; smooth ER, which acts in lipid synthesis and protein secretion, resembles tubes. The ER protein AMP1, she said, is anchored in the rough ER.
"My lab has been conducting research on AMP1 for many years," she said. "And it's this protein that drew our attention to the ER. First, we realized that AMP1 is involved in miRNA-mediated translational inhibition. Then, since we already knew that AMP1 is localized in the rough ER, we shifted our focus to this organelle."
Next, her lab will attempt to crack the mechanism of miRNA-mediated translational inhibition. They will investigate, too, how miRNAs are recruited to the ER.
Chen was joined in the study by Shengben Li (first author of the research paper), Lin Liu, Xigang Liu, Yu Yu, Lijuan Ji and Natasha Raikhel at UC Riverside; Xiaohong Zhuang and Liwen Jiang at the Chinese University of Hong Kong; Xia Cui and Xiaofeng Cao at the Chinese Avademy of Sciences, Beijing; Zhiqiang Pan at the University of Mississippi; Beixin Mo at Shenzhen University, China; and Fuchun Zhang at Xinjiang University, China.
The study was supported by grants to Chen from the National Institutes of Health, the National Science Foundation, and the Howard Hughes Medical Institute and Gordon and Betty Moore Foundation.
The University of California, Riverside is a doctoral research university, a living laboratory for groundbreaking exploration of issues critical to Inland Southern California, the state and communities around the world. Reflecting California's diverse culture, UCR's enrollment has exceeded 21,000 students. The campus will open a medical school in 2013 and has reached the heart of the Coachella Valley by way of the UCR Palm Desert Center. The campus has an annual statewide economic impact of more than $1 billion. A broadcast studio with fiber cable to the AT&T Hollywood hub is available for live or taped interviews. UCR also has ISDN for radio interviews. To learn more, call (951) UCR-NEWS.
Iqbal Pittalwala | EurekAlert!
22.02.2018 | Albert-Ludwigs-Universität Freiburg im Breisgau
Separate brain systems cooperate during learning, study finds
22.02.2018 | Brown University
Quantum computers may one day solve algorithmic problems which even the biggest supercomputers today can’t manage. But how do you test a quantum computer to...
For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.
In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...
Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale
Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...
For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.
But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...
Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.
The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...
15.02.2018 | Event News
13.02.2018 | Event News
12.02.2018 | Event News
22.02.2018 | Life Sciences
22.02.2018 | Physics and Astronomy
22.02.2018 | Earth Sciences