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G-quadruplexes (G4s) are secondary DNA and RNA structures stabilized by positive cations in a central channel formed by stacked tetrads of Hoogsteen base-paired guanines. G4s form from G-rich sequences across the genome, whose biased distribution in regulatory regions points towards a gene-regulatory role. G4s can themselves be regulated by helicases, such as DHX36 (aliases: G4R1 and RHAU), which possess the necessary activity to resolve these stable structures. G4s have been shown to both positively and negatively regulate gene expression when stabilized by ligands, or through the loss of helicase activity. Using DHX36 knockout Jurkat cell lines, we identified widespread, although often subtle, effects on gene expression that are associated with the presence or number of observed G-quadruplexes in promoters or gene regions. Genes that significantly change their expression, particularly those that show a significant increase in RNA abundance under DHX36 knockout, are associated with a range of cellular functions and processes, including numerous transcription factors and oncogenes, and are linked to several cancers. Our work highlights the direct and indirect role of DHX36 in the transcriptome of T-lymphocyte leukemia cells and the potential for DHX36 dysregulation in cancer. [ABSTRACT FROM AUTHOR]

DEAH/RHA helicases are members of a large group of proteins collectively termed DExH-box, which also include Ski2-like and NS3/NPH-II helicases. By binding and remodeling DNA and RNA, DEAH/RHA helicases play critical roles in many cellular processes ranging from transcription and splicing to ribosome biogenesis, innate immunity and stress granule formation. While numerous crystal structures of other DExH-box proteins helicases have been reported, no structures of DEAH/RHA helicases bound to nucleic acid substrates have been available until the recent co-crystal structures of the maleless (MLE) and Prp43p bound to RNA. This review examines how these new structures provide a starting point to understand how DEAH/RHA helicases bind to, translocate on, and unwind nucleic acid substrates. [ABSTRACT FROM AUTHOR]

DExD (DDX)- and DExH (DHX)-box RNA helicases, named after their Asp-Glu-x-Asp/His motifs, are integral to almost all RNA metabolic processes in eukaryotic cells. They play myriad roles in processes ranging from transcription and mRNA-protein complex remodeling, to RNA decay and translation. This last facet, translation, is an intricate process that involves DDX/DHX helicases and presents a regulatory node that is highly targetable. Studies aimed at better understanding this family of conserved proteins have revealed insights into their structures, catalytic mechanisms, and biological roles. They have also led to the development of chemical modulators that seek to exploit their essential roles in diseases. Herein, we review the most recent insights on several general and target-specific DDX/DHX helicases in eukaryotic translation initiation. [ABSTRACT FROM AUTHOR]