Probable ATP-dependent RNA helicase DHX36 also known as DEAH box protein 36 (DHX36) or MLE-like protein 1 (MLEL1) or G4 resolvase 1 (G4R1) or RNA helicase associated with AU-rich elements (RHAU) is an enzyme that in humans is encoded by the DHX36 gene. [4] [5]
Structurally, DHX36 is a 1008 amino acid-long modular protein that has been crystallized in a complex with a DNA G-quadruplex. [6] It consists of a ~440-amino acid helicase core comprising all signature motifs of the DEAH/RHA family of helicases with N- and C-terminal flanking regions of ~180 and ~380 amino acids, respectively. Part of the N-terminal flanking region forms an alpha-helix called the DHX36-specific motif, which recognizes the 5'-most G-quadruplex quartet. The OB-fold domain binds to the 3'-most G-tract sugar-phosphate backbone. [7] Like all the DEAH/RHA helicases, the helicase associated domain is located adjacent to the helicase core region and occupies 75% of the C-terminal region. [8]
DEAH/RHA proteins are RNA and DNA helicases typically characterized by low processivity translocation on substrates and the capability to bind/unwind non-canonical nucleic acid secondary structures. [9] They are implicated in a number of cellular processes involving alteration of RNA secondary structure such as translation initiation, nuclear and mitochondrial splicing, and ribosome and spliceosome assembly. Based on their distribution patterns, some members of this DEAH/RHA protein family are believed to be involved in embryogenesis, spermatogenesis, and cellular growth and division. [4]
DHX36 exhibits a unique ATP-dependent guanine-quadruplex (G4) resolvase activity and specificity for its substrate in vitro. [10] [11] DHX36 displays repetitive unwinding activity as a function of the thermal stability of the G-quadruplex substrate, characteristic of a number of other G-quadruplex resolvases such as the BLM/WRN helicases. [12] [13] DHX36 binds G4-nucleic acid with sub-nanomolar affinity and unwinds G4 structures much more efficiently than double-stranded nucleic acid. Consistent with these biochemical observations, DHX36 was also identified as the major source of tetramolecular RNA-resolving activity in HeLa cell lysates.
Previous work showed that DHX36 associates with mRNAs and re-localises to stress granules (SGs) upon translational arrest induced by various environmental stresses. [14] [15] A region of the first 105 amino acid was shown to be critical for RNA binding and re-localisation to SGs.
DNA primase is an enzyme involved in the replication of DNA and is a type of RNA polymerase. Primase catalyzes the synthesis of a short RNA segment called a primer complementary to a ssDNA template. After this elongation, the RNA piece is removed by a 5' to 3' exonuclease and refilled with DNA.
In a chain-like biological molecule, such as a protein or nucleic acid, a structural motif is a common three-dimensional structure that appears in a variety of different, evolutionarily unrelated molecules. A structural motif does not have to be associated with a sequence motif; it can be represented by different and completely unrelated sequences in different proteins or RNA.
Helicases are a class of enzymes thought to be vital to all organisms. Their main function is to unpack an organism's genetic material. Helicases are motor proteins that move directionally along a nucleic acid phosphodiester backbone, separating two hybridized nucleic acid strands, using energy from ATP hydrolysis. There are many helicases, representing the great variety of processes in which strand separation must be catalyzed. Approximately 1% of eukaryotic genes code for helicases.
A Hoogsteen base pair is a variation of base-pairing in nucleic acids such as the A•T pair. In this manner, two nucleobases, one on each strand, can be held together by hydrogen bonds in the major groove. A Hoogsteen base pair applies the N7 position of the purine base and C4 amino group, which bind the Watson–Crick (N3–C4) face of the pyrimidine base.
Werner syndrome ATP-dependent helicase, also known as DNA helicase, RecQ-like type 3, is an enzyme that in humans is encoded by the WRN gene. WRN is a member of the RecQ Helicase family. Helicase enzymes generally unwind and separate double-stranded DNA. These activities are necessary before DNA can be copied in preparation for cell division. Helicase enzymes are also critical for making a blueprint of a gene for protein production, a process called transcription. Further evidence suggests that Werner protein plays a critical role in repairing DNA. Overall, this protein helps maintain the structure and integrity of a person's DNA.
In molecular biology, G-quadruplex secondary structures (G4) are formed in nucleic acids by sequences that are rich in guanine. They are helical in shape and contain guanine tetrads that can form from one, two or four strands. The unimolecular forms often occur naturally near the ends of the chromosomes, better known as the telomeric regions, and in transcriptional regulatory regions of multiple genes, both in microbes and across vertebrates including oncogenes in humans. Four guanine bases can associate through Hoogsteen hydrogen bonding to form a square planar structure called a guanine tetrad, and two or more guanine tetrads can stack on top of each other to form a G-quadruplex.
In biochemistry, two biopolymers are antiparallel if they run parallel to each other but with opposite directionality (alignments). An example is the two complementary strands of a DNA double helix, which run in opposite directions alongside each other.
DNA replication licensing factor MCM4 is a protein that in humans is encoded by the MCM4 gene.
DEAD box proteins are involved in an assortment of metabolic processes that typically involve RNAs, but in some cases also other nucleic acids. They are highly conserved in nine motifs and can be found in most prokaryotes and eukaryotes, but not all. Many organisms, including humans, contain DEAD-box (SF2) helicases, which are involved in RNA metabolism.
ATP-dependent RNA helicase A is an enzyme that in humans is encoded by the DHX9 gene.
Probable ATP-dependent RNA helicase DDX5 also known as DEAD box protein 5 or RNA helicase p68 is an enzyme that in humans is encoded by the DDX5 gene.
ATP-dependent DNA helicase Q1 is an enzyme that in humans is encoded by the RECQL gene.
Pre-mRNA-splicing factor ATP-dependent RNA helicase PRP16 is an enzyme that in humans is encoded by the DHX38 gene.
The eukaryotic initiation factor-4A (eIF4A) family consists of 3 closely related proteins EIF4A1, EIF4A2, and EIF4A3. These factors are required for the binding of mRNA to 40S ribosomal subunits. In addition these proteins are helicases that function to unwind double-stranded RNA.
Nucleic acid secondary structure is the basepairing interactions within a single nucleic acid polymer or between two polymers. It can be represented as a list of bases which are paired in a nucleic acid molecule. The secondary structures of biological DNAs and RNAs tend to be different: biological DNA mostly exists as fully base paired double helices, while biological RNA is single stranded and often forms complex and intricate base-pairing interactions due to its increased ability to form hydrogen bonds stemming from the extra hydroxyl group in the ribose sugar.
RHAU is a 114-kDa human RNA helicase of the DEAH-box family of helicases encoded by the DHX36 gene.
Protein ZGRF1 is a protein encoded in the human by the ZGRF1 gene also known as C4orf21, that has a weight of 236.6 kDa. The ZGRF1 gene product localizes to the cell nucleus and promotes DNA repair by stimulating homologous recombination. This gene shows relatively low expression in most human tissues, with increased expression in situations of chemical dependence. ZGRF1 is orthologous to nearly all eukaryotes. Functional domains of this protein link it to a series of helicases, most notably the AAA_12 and AAA_11 domains.
RRM3 is a gene that encodes a 5′-to-3′ DNA helicase known affect multiple cellular replication and repair processes and is most commonly studied in Saccharomyces cerevisiae. RRM3 formally stands for Ribosomal DNArecombination mutation 3. The gene codes for nuclear protein Rrm3p, which is 723 amino acids in length, and is part of a Pif1p DNA helicase sub-family that is conserved from yeasts to humans. RRM3 and its encoded protein have been shown to be vital for cellular replication, specifically associating with replication forks genome-wide. RRM3 is located on chromosome 8 in yeast cells and codes for 723 amino acids producing a protein that weighs 81,581 Da.
DExH-box helicase 29 (DHX29) is a 155 kDa protein that in humans is encoded by the DHX29 gene.
PIF1 5'-to-3' DNA helicase is a protein that in humans is encoded by the PIF1 gene.
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