DHX36 (DEAH-Box Helicase 36), also known as G4RNA helicase or G4R1, is a member of the DEAH-box family of RNA helicases that recognizes and resolves G-quadruplex (G4) structures in both DNA and RNA. This ATP-dependent helicase plays critical roles in regulating gene expression at multiple levels, including transcription, mRNA translation, and RNA stability. DHX36 has emerged as an important factor in neurodegenerative diseases, particularly Amyotrophic Lateral Sclerosis (ALS), where G-quadruplex dysregulation contributes to RNA metabolism defects.
DHX36 is a ~114 kDa protein composed of multiple functional domains that enable its diverse functions:
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DHX36 — DEAH-Box Helicase 36
Introduction
DHX36 (DEAH-Box Helicase 36), also known as G4RNA helicase or G4R1, is a member of the DEAH-box family of RNA helicases that recognizes and resolves G-quadruplex (G4) structures in both DNA and RNA. This ATP-dependent helicase plays critical roles in regulating gene expression at multiple levels, including transcription, mRNA translation, and RNA stability. DHX36 has emerged as an important factor in neurodegenerative diseases, particularly Amyotrophic Lateral Sclerosis (ALS), where G-quadruplex dysregulation contributes to RNA metabolism defects.
DHX36 is a ~114 kDa protein composed of multiple functional domains that enable its diverse functions:
Core Helicase Domains
DEAH motif: The characteristic DEAH-box helicase core contains nine conserved motifs (Motifs I-VI, Ia, Ib, and Q motif) essential for ATP binding and hydrolysis[@bourbigot2020]
RecA-like domains: Two RecA-like domains form the helicase motor that couples ATP hydrolysis to nucleic acid unwinding
C-terminal domain: A specialized domain required for G-quadruplex recognition
G-Quadruplex-Binding Domain
The unique C-terminal region of DHX36 contains a specific G4-binding domain (G4BD) that distinguishes it from other DEAH-box helicases. This domain specifically recognizes parallel G-quadruplex structures with high affinity[@mauger2015].
Molecular Functions
G-Quadruplex Resolution
DHX36 is one of the most efficient G-quadruplex unwinding enzymes identified to date[@vaughn2015]. G-quadruplexes are four-stranded DNA/RNA structures formed by stacks of guanine tetrads, which can form in G-rich promoter regions, telomeres, and RNA transcripts. DHX36 resolves these structures through:
Direct recognition: The G4BD domain binds specifically to G4 structures
ATP-dependent unwinding: The helicase core uses ATP hydrolysis to destabilize G4 stems
Product release: Unwound single strands are released for downstream processing
Transcription Regulation
DHX36 regulates transcription through multiple mechanisms[@takahama2013]:
Promoter G4 resolution: Resolves G4 structures in gene promoters to facilitate transcription initiation
Transcriptional elongation: Affects RNA polymerase II processivity through G4 clearance
Chromatin association: Associates with chromatin at G-rich regulatory elements
mRNA Translation
DHX36 modulates mRNA translation at multiple levels[@frye2018]:
Translation initiation: Regulates 5' UTR G4-mediated translation control
Ribosome recruitment: Facilitates ribosomal scanning through structured 5' regions
Alternative translation: Enables cap-independent translation of specific mRNAs
Cellular Pathways and Interactions
Stress Granule Formation
DHX36 is recruited to stress granules (SGs)—membrane-less organelles formed during cellular stress[@japot2018]. In stress conditions:
DHX36 associates with SG marker proteins like G3BP1
G4 structures accumulate in stalled mRNPs, requiring DHX36 for resolution
DHX36 deficiency leads to SG assembly defects
RNA Processing
DHX36 participates in multiple RNA processing pathways:
Pre-mRNA splicing: Associates with spliceosome components
Non-coding RNA processing: Handles miRNA and siRNA precursors
Protein-Protein Interactions
Key interaction partners include:
G3BP1/2: Stress granule assembly factors
PABPC1: Poly(A)-binding protein
FUS: RNA-binding protein mutated in ALS
[TDP-43](/mechanisms/tdp-43-proteinopathy): RNA-binding protein central to ALS pathology
Disease Associations
Amyotrophic Lateral Sclerosis (ALS)
DHX36 variants have been associated with increased ALS risk[@chen2020][@sznajder2018]. The mechanistic link involves:
RNA metabolism defects: ALS-associated mutations disrupt G4 resolution, leading to RNA processing abnormalities
Stress granule dynamics: DHX36 dysfunction alters SG formation and clearance in motor [neurons](/entities/neurons)
Axonal RNA transport: G4-dependent mRNA localization is impaired in motor neurons
Protein aggregation: Dysregulated RNA metabolism contributes to toxic protein aggregation
RTTN (Rotated Tawny Navel)
While primarily associated with a rare developmental disorder, RTTN involves neural progenitor cell dysfunction where DHX36's role in cell division and gene regulation may be relevant.
Neurodegeneration Mechanisms
The broader connection between DHX36 and neurodegeneration involves[@silva2019]:
Genomic instability: G4 dysregulation leads to DNA damage accumulation