The gene spans 48.5 kb and is composed of 27 exons.

Transcription start is 163 bp upstream of first ATG of the DHX9 ORF. The translation start site is located in exon 2 and there is a sole isoform ubiquitously expressed.

DHX9 pseudogene (DHX9P) is located at 13q22.

Monomeric 140 kDa protein. Human DHX9 is 1270 amino acids. It contains an helicase catalytic domain flanked by two double-stranded RNA binding domains (dsRBD) at the N-terminus and an RGG-box at the C terminus. A bidirectional nuclear transport domain is located at the C terminus.

All tissues tested, ubiquitous expression.

DHX9 shuttles between the nucleus and the cytoplasm.

DHX9 is a nucleic-acid helicase that unwinds double-stranded DNA and RNA in a nucleotide dependent manner. It acts as a transcriptional coactivator which stimulates transcription by interacting with the transcriptional coactivator CBP/p300, the breast cancer protein BRCA1, the RNA polymerase II and has an important role in the assembly of STAT6 transcriptosome.
DHX9 plays a role in regulating chromatin structure by interacting physically and functionally with topoisomerase IIa.
It mediates the attachment of nuclear ribonucleoprotein complexes to actin filaments, which may be related to RNA processing and transport. DHX9 interacts with the survival motor neuron which plays a role in the assembly and regeneration of small nuclear ribonucleoproteins and spliceosomes.
DHX9 acts as a nuclear shuttle protein promoting the export of mRNA transcripts through binding to TAP and HAP95.
In the cytoplasm, DHX9 is preferentially associated with actively translating polyribosomes and is necessary for efficient translation of RNAs that contain a highly structured 5UTR.
DHX9 might be necessary for maintaining genomic stability as it plays a role in promoting the DNA processing function of WRN. Overexpression of a truncated DHX9 peptide prevents normal BRCA1 function, such as BRCA1 association with nuclear foci following DNA damage. DHX9 associates with gH2AX after DNA damage, suggesting a role for DHX9 in DNA repair.
DHX9 is also necessary for early embryonic development in mice.

Sequence analysis revealed that DHX9 contains seven helicase core motifs that are conserved among the DEX[D/H] helicase superfamily. DHX9 is highly conserved among man, cow, mouse, worm, and fruit fly.

DHX9 truncating mutations were reported to affect the interaction with BRCA1 and RNA polymerase II, and to result in decreased transcriptional activity of BRCA1.
In mammals, DHX9-knockout mice are embryonic lethal for homozygous DHX9 mutants. DHX9 is thus necessary for early embryonic development in mice. It was also suggested that DHX9 is required for the survival and differentiation of embryonic ectoderm.
DHX9 maps to chromosome 1q25 near a major susceptibility locus for prostate cancer.