Alternative titles; symbols
HGNC Approved Gene Symbol: DDX56
Cytogenetic location: 7p13 Genomic coordinates (GRCh38): 7:44,565,804-44,573,908 (from NCBI)
DDX56 belongs to the DEAD box family of ATP-dependent RNA helicases. It shows ATPase activity in the presence of polynucleotides and associates with nucleoplasmic 65S preribosomal particles (Zirwes et al., 2000).
By screening keratinocyte and HeLa cell cDNA expression libraries, Zirwes et al. (2000) cloned DDX56, which they designated NOH61. The deduced 547-amino acid protein has a calculated molecular mass of 61.5 kD. DDX56 contains the 9-motif helicase core region, including a central DEAD box, conserved in DEAD box proteins. In addition, it has a leucine zipper motif in its N-terminal third, 2 putative C-terminal nuclear localization signals, one monopartite and the other bipartite, and several potential phosphorylation sites. Northern blot analysis of HeLa cells, a keratinocyte cell line, and several human tissues detected ubiquitous expression of a 2.0-kb transcript. In vitro transcription and translation in a reticulocyte lysate system yielded a protein of about 61 kD. DDX56 was detected in total HeLa cell lysates and was significantly enriched in the nuclear and nucleolar fractions. Immunofluorescence microscopy and immunoelectron microscopy revealed enriched expression of DDX56 in nucleoli and weak labeling of the nucleoplasm.
Zirwes et al. (2000) demonstrated that recombinant DDX56 expressed in E. coli was an active ATPase in the presence of various polynucleotides in vitro. Endogenous HeLa cell DDX56 sedimented as a homooligomeric structure that was disrupted by hypertonic salts. DDX56 was also a constituent of free nucleoplasmic 65S preribosomal particles, but it was absent from cytoplasmic ribosomes. Treatment of cells with a transcription inhibitor and RNase A resulted in complete dissociation of DDX56 from nucleolar structures. Zirwes et al. (2000) hypothesized that DDX56 may be involved in ribosome synthesis, most likely during assembly of the large 60S ribosomal subunit.
The International Radiation Hybrid Mapping Consortium mapped the DDX56 gene to chromosome 7 (SHGC-5634).
Zirwes, R. F., Eilbracht, J., Kneissel, S., Schmidt-Zachmann, M. S. A novel helicase-type protein in the nucleolus: protein NOH61. Molec. Biol. Cell 11: 1153-1167, 2000. [PubMed: 10749921] [Full Text: https://doi.org/10.1091/mbc.11.4.1153]