DNAJB1

Researchers have translated a cutting-edge tactic for treating genetic disorders into a fresh approach for potentially stymying cancer. Cell division is the generative spark of nearly every lifeform on Earth. But if healthy growth goes unchecked, cell division can turn lethal, overwhelming the organism. Such is the case with so-called oncogenes. When altered by a mutation, these growth-moderating genes go haywire, producing a geyser of cancer cells as a result. Oncogenes are also insidiously adept at generating tumors that over time become genetically "independent" from their origin, so it has been exceedingly difficult for scientists to shut down their replication at the source. Now Rockefeller University researchers have discovered a new way to target the oncogene behind a rare and often deadly liver disease using small interfering RNAs (siRNAs), an innate mechanism for silencing gene expression. As described in Molecular Therapy, the researchers slipped siRNAs inside fibrolamellar hepatocellular carcinoma (FLC) cells through a surface receptor, where they blocked the oncogene from producing illness-inducing proteins that lead to tumor formation. It's the first time that siRNAs have been used to hobble the progression of FLC, says first author Christoph Neumayer, a Ph.D. student in Rockefeller's Laboratory of Cellular Biophysics, headed by Sanford M. Simon. But the findings have wider applications as well. "That's the really exciting part," says Neumayer. "This is proof of concept that siRNAs can be used for FLC, as well as adult liver cancers, which are much more common, and other tumor types elsewhere in the body." The fusion oncogene FLC is caused by the fusion of two genes located on chromosome 19: DNAJB1, which produces heat-shock proteins that encourage cell homeostasis, and PRKACA, which produces an enzyme called kinase A that's key to cellular metabolic function. The resulting fusion, known as DNAJB1::PRKACA, brings together the proteins and a catalytic subunit of the kinase. This dysfunctional union promotes FLC formation, but how, exactly, is still unknown. Researchers in Simon's lab discovered that this fusion caused FLC in 2014, several years after Simon's own teenage daughter, Elana, was diagnosed with liver disease. After having the resulting tumor removed -- the only treatment option available to people with FLC -- Elana went on to collaborate with her father to unearth its cause, publishing the results in Science. Since then, Simon and his group have continued to reveal the mechanisms behind the disease as well as develop therapeutics. The siRNA research is part of a three-part strategy which also includes repurposing drugs for treating FLC and using molecules known as PROTACs to selectively degrade the DNAJB1::PRKACA protein that drives FLC. The drug repurposing is in advanced preparation for a clinical trial, and some of the PROTAC work is part of an international collaboration that was just awarded a $25 million Cancer Grand Challenges grant to develop treatments for high-risk, oncogene-driven cancers in children. Recently, Simon's lab discovered that they could completely stop FLC tumor growth in mice using shRNAs, short sequences of RNA that can be engineered to disrupt mRNA. The approach also caused many tumors to shrink or disappear. Having shown that quelling the fused oncogene killed tumor cells, they decided to experiment with derailing kinase A activity, which research indicated was driving tumor growth. Unlocking the cell door The problem was, fused kinase A and its "wild type" form are nearly identical, so "any drug you developed that blocks fused kinase A activity would affect all kinase A, including in normal cells," Neumayer says. "In other words, you would incur a host of problematic side effects." They had to find a way to disable toxic kinase while containing the impact so that kinase in other cells weren't affected. To do that, they specifically designed siRNAs to aim at the fusion. But because siRNAs cannot cross cell membranes, the researchers needed to figure out a way to get the siRNA inside. Luckily, a door into the cell had already been identified: a receptor called ASGR1 that's only expressed in liver cells. Its key had been too: a binding molecule known as GalNAc. Together, the duo function as a waste disposal team. GalNAc conjugate therapies, which attach siRNA molecules to the ligand to deliver therapies inside cells, are already on the market for conditions such as hereditary transthyretin-mediated amyloidosis and atherosclerotic cardiovascular disease. The team wondered if they could use the same approach to thwart the kinase driving FLC tumors. Stabilization and shrinkage To test their theory, the researchers attached a custom siRNA to the receptor's ligand and studied the method in a variety of tumor models in mice and in human cell cultures. The conjugate therapy was not only successfully delivered into the cells in all contexts, but it also caused a reduction of mRNA in the oncogene, preventing the production of the protein and resulting in the tumors stagnating or shrinking, unable to grow. They also did not detect any liver toxicity in the mice, indicating the animals tolerated the siRNAs well. "What we saw was tumor inhibition, when we had hoped to outright kill the tumor," Neumayer notes. "Our future direction will be to try to figure out how to improve that." They also tested the specificity of the siRNA by injecting it into tumor cells of another type of liver cancer. It had no toxic impact on them -- exactly as the researchers hoped. "We wanted to show that our siRNA is so targeted to the FLC fusion oncogene that it has no side effects on other cells -- even on other cancer cells," he notes. Neumayer says the findings suggest that siRNAs may be effective beyond FLC, capable of treating tumors throughout the body with a high degree of specificity: "I think siRNA medicines as a class will have a big impact over time as a new kind of genetic therapy."

A team deciphers complicated mechanism underlying genetic diversity. Movies such as 'X-Men,' 'Fantastic Four,' and 'The Guardians,' which showcase vibrant mutant heroes, have captivated global audiences. Recently, a high-throughput genetic screening of meiotic crossover rate mutants in Arabidopsis thaliana garnered the interest of the academic community by unraveling a century-old mystery in the life sciences. A research team, consisting of Professor Kyuha Choi, Dr. Jaeil Kim, and PhD candidate Heejin Kim from the Department of Life Sciences at Pohang University of Science and Technology (POSTECH), has achieved a remarkable feat by unveiling the molecular mechanism responsible for crossover interference during meiosis, a biological pattern at the chromosome level. The findings of this research were published on February 20 in Nature Plants, an international journal in the field of life sciences. In sexually reproducing organisms, individuals resemble their parents or siblings. Despite the striking similarities, it's crucial to recognize that absolute identicalness is unattainable. This variation is attributed to the process of meiosis, which generates reproductive cells like sperm and eggs in animals or pollen and ovules in plants. Unlike somatic cell division, which duplicates and divides the genome identically, meiosis creates genetically diverse reproductive cells through a mechanism known as crossover. Meiosis and crossover play pivotal roles in biodiversity and have significant implications in breeding where the selection and cultivation of superior traits in crops occur. Typically, most animal and plant species exhibit a minimum of one and a maximum of three crossovers per a pair of homologous chromosomes. The ability to control the number of these crossovers could lead to cultivating crops with specific desired traits. However, achieving such control has been challenging due to the 'phenomenon of crossover interference.' Crossover interference, where one crossover inhibits the formation of another crossover nearby along the same chromosome, was initially identified by fruit fly geneticist Hermann J. Muller in 1916. Despite researchers' persistent efforts over the past century since its discovery, it is only recently that the mechanisms underlying crossover interference have started to unveil their secrets. In this research, the team utilized a high-throughput fluorescent seed scoring method to directly measure crossover frequency in Arabidopsis plants. Through a genetic screen, they identified a mutant named hcr3 (high crossover rate3) that exhibited an increased crossover rate at the genomic level. Further analysis revealed that the elevated crossovers in hcr3 was attributed to a point mutation in the J3 gene, which encodes a co-chaperone related to HSP40 protein. This research demonstrated that a network involving HCR3/J3/HSP40 co-chaperone and the chaperone HSP70 controls crossover interference and localization by facilitating the degradation of the pro-crossover protein, HEI10 ubiquitin E3 ligase. The application of genetic screen approaches to uncover the crossover interference and inhibition pathway successfully addressed a century-old puzzle in the life sciences. POSTECH Professor Kyuha Choi stated, "Applying this research to agriculture will enable us to rapidly accumulate beneficial traits, thereby reducing breeding time." He expressed optimism by saying, "We hope this research will contribute to the breeding of new varieties and identification of useful natural variations responsible for desirable traits such as disease and environmental stress resistance, improved productivity, and high-value production." The research was conducted with support from the Basic Research Program in Science and Engineering and the Mid-Career Researcher Program of the National Research Foundation of Korea, the Next-Generation BioGreen 21 Program of the Rural Development Administration, the Suh Kyungbae Foundation, and the Samsung Science & Technology Foundation.