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Published on: November 1, 2012
DDX43 prefers single strand substrate and its full binding activity requires physical connection of all domains
Han Wu1, Liu-Tao Zhai1, Peng-Yang Chen1
1State Key Laboratory of Crop Stress Biology in Arid Areas, College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, 712100, China.
Abstract:
DDX43 is a cancer/testis antigen and is thought to stimulate oncogenic pathways in cell proliferation, while its specific function in cancer development is largely unexplored. DDX43 is the member of RNA helicase in DEAD-box family, consists of conserved helicase core and a single K-homology (KH) domain in its N-terminus. In this paper, we expressed and purified human DDX43 protein in E. coli and demonstrated that this protein is a homogeneous monomer. To understand the role and explore the substrates preference of DDX43 in vitro, we systematically studied its binding properties. We found that DDX43 prefers single-strand DNA or RNA with length longer than 12 nt and much prefers guanosine than the other three nucleotides. Achievement of the full binding affinity of protein to substrate needs the existence of all domains, and they must be connected. The absence of either of them or the disjunction can result in a decreased binding affinity to substrates, approximately reduced 10-fold. We also found that the unwinding ability of DDX43 in vitro was neither efficient nor sustainable.
Insights
The DEAD-box RNA helicase DDX43, a cancer-testis antigen, binds single-stranded DNA/RNA longer than 12 nucleotides, preferring guanosine. Its full binding requires intact domains, and its unwinding ability is limited.
Area of Science:
- Molecular Biology
- Biochemistry
- Cancer Research
Background:
- DDX43 is a cancer/testis antigen implicated in oncogenic pathways.
- Its precise role in cancer development remains largely unknown.
- DDX43 belongs to the DEAD-box RNA helicase family, featuring a conserved helicase core and an N-terminal K-homology (KH) domain.
Purpose of the Study:
- To characterize the biochemical properties of human DDX43.
- To investigate the substrate preference and binding characteristics of DDX43 in vitro.
- To elucidate the functional importance of DDX43's domains for substrate binding.
Main Methods:
- Expression and purification of recombinant human DDX43 protein in E. coli.
- In vitro binding assays to determine substrate preference (DNA/RNA length and nucleotide composition).
- Analysis of domain integrity's impact on protein-substrate binding affinity.
Main Results:
- Purified DDX43 exists as a homogeneous monomer.
- DDX43 exhibits a preference for single-stranded DNA/RNA longer than 12 nucleotides.
- The protein shows a strong preference for guanosine over other nucleotides.
- Full binding affinity requires all domains to be present and connected; domain absence or disjunction reduces affinity ~10-fold.
- DDX43 demonstrates inefficient and unsustainable in vitro RNA unwinding activity.
Conclusions:
- DDX43's substrate binding is dependent on its structural integrity.
- The RNA helicase activity of DDX43 is limited, suggesting roles beyond simple unwinding.
- Further research is needed to fully understand DDX43's function in cancer development.
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