83 research outputs found
Wnt signaling in triple-negative breast cancer
Wnt signaling regulates a variety of cellular processes, including cell fate, differentiation, proliferation and stem cell pluripotency. Aberrant Wnt signaling is a hallmark of many cancers. An aggressive subtype of breast cancer, known as triple-negative breast cancer (TNBC), demonstrates dysregulation in canonical and non-canonical Wnt signaling. In this review, we summarize regulators of canonical and non-canonical Wnt signaling, as well as Wnt signaling dysfunction that mediates the progression of TNBC. We review the complex molecular nature of TNBC and the emerging therapies that are currently under investigation for the treatment of this disease
Native Variants of the MRB1 Complex Exhibit Specialized Functions in Kinetoplastid RNA Editing
We want to thank Kathy Kyler for editing this manuscript, Ken Stuart for supplying monoclonal antisera against RECC subunits, and Laurie K. Read for her gift of polyclonal antisera against GAP1 and RGG2. Funding: National Science Foundation Grant No. NSF1122109 (PI: J.Cruz-Reyes.). NIH/National Institute of Allergies and Infectious Diseases R01 AI088011 (PI: Blaine Mooers). Institutional Development Award (IDeA) from the National Institute of General Medical Sciences of the National Institutes of Health under grant number P20 GM103640. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Adaptation and survival of Trypanosoma brucei requires editing of mitochondrial mRNA by uridylate (U) insertion and deletion. Hundreds of small guide RNAs (gRNAs) direct the mRNA editing at over 3,000 sites. RNA editing is controlled during the life cycle but the regulation of substrate and stage specificity remains unknown. Editing progresses in the 3’ to 5’ direction along the pre-mRNA in blocks, each targeted by a unique gRNA. A critical editing factor is the mitochondrial RNA binding complex 1 (MRB1) that binds gRNA and transiently interacts with the catalytic RNA editing core complex (RECC). MRB1 is a large and dynamic complex that appears to be comprised of distinct but related subcomplexes (termed here MRBs). MRBs seem to share a ‘core’ complex of proteins but differ in the composition of the ‘variable’ proteins. Since some proteins associate transiently the MRBs remain imprecisely defined. MRB1 controls editing by unknown mechanisms, and the functional relevance of the different MRBs is unclear. We previously identified two distinct MRBs, and showed that they carry mRNAs that undergo editing. We proposed that editing takes place in the MRBs because MRBs stably associate with mRNA and gRNA but only transiently interact with RECC, which is RNA free. Here, we identify the first specialized functions in MRBs: 1) 3010-MRB is a major scaffold for RNA editing, and 2) REH2-MRB contains a critical trans-acting RNA helicase (REH2) that affects multiple steps of editing function in 3010-MRB. These trans effects of the REH2 include loading of unedited mRNA and editing in the first block and in subsequent blocks as editing progresses. REH2 binds its own MRB via RNA, and conserved domains in REH2 were critical for REH2 to associate with the RNA and protein components of its MRB. Importantly, REH2 associates with a ~30 kDa RNA-binding protein in a novel ~15S subcomplex in RNA-depleted mitochondria. We use these new results to update our model of MRB function and organization.Yeshttp://www.plosone.org/static/editorial#pee
Recommended from our members
Mechanistic studies of the RNA chaperone activities of the DEAD-box RNA helicase CYT-19
textStructured RNAs are pervasive in biology, spanning a functional repertoire that includes messengers, regulators of gene expression and catalysts of translation and splicing. From the relatively simple tRNAs and riboswitches to the highly structured ribosomal RNAs, the ability of RNAs to function is dependent on well-defined secondary and tertiary structures. However, studies of RNA folding in vitro have revealed an extreme propensity to form alternative structures, which can be long-lived and interfere with function. In the cell, a diverse array of RNA binding proteins and RNA chaperones guide RNAs towards the correct structure and disrupt misfolded intermediates. Among these proteins, DEAD-box protein family stands out as one of the largest groups, with its members ubiquitously involved in RNA metabolism across all domains of life. DEAD-box proteins can function as both specific and general RNA chaperones by disrupting RNA structures in an ATP-dependent manner. Here I describe my work studying the general RNA chaperone mechanism of the Neurospora crassa protein CYT-19, a model DEAD-box protein and a biological RNA chaperone that is required for efficient folding of self-splicing group I intron RNAs in vivo. After an introduction to DEAD-box proteins and their mechanisms as RNA remodelers (Chapter 1), I will first describe studies of group I intron unfolding by CYT-19, focusing on the effects of RNA tertiary structure stability on CYT-19 activity and targeting to RNA substrates (Chapter 2). I will then describe the characterization of ATP-dependent mechanisms during CYT-19-mediated refolding of the misfolded group I intron (Chapter 3). In Chapter 4, I will present small-angle X-ray scattering (SAXS) studies of structural features of DEAD-box proteins that allow them to efficiently interact with large structured RNA substrates. Finally, I will turn to studies of DEAD-box protein involvement during early steps of RNA compaction and folding, using SAXS and activity-based approaches (Chapter 5). I will conclude with a general discussion of superfamily 2 RNA helicases, which include DEAD-box and related proteins, and their functions and mechanisms as remodelers of structured RNAs and RNPs.Biochemistr
Lessons from Enzyme Kinetics Reveal Specificity Principles for RNA-Guided Nucleases in RNA Interference and CRISPR-Based Genome Editing
- …