NCBI Summary:
DEAD box proteins, characterized by the conserved motif Asp-Glu-Ala-Asp (DEAD), are putative RNA helicases. 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 family are believed to be involved in embryogenesis, spermatogenesis, and cellular growth and division. This gene includes 2 alternatively spliced transcripts encoding 2 different isoforms. The larger isoform is a DEAD box protein with RNA helicase activity. It may participate in melting of DNA:RNA hybrids, such as those that occur during transcription, and may play a role in X-linked gene expression. It contains 2 copies of a double-stranded RNA-binding domain, a DEXH core domain and an RGG box. The RNA-binding domains and RGG box influence and regulate RNA helicase activity. The smaller isoform is a lymphocyte granule protein. It lacks RNA-binding domains and DEXH core domain, but contains an RGG box, which may render this isoform RNA binding function.
General function
Cell proliferation, RNA processing, RNA binding
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Cellular localization
Cytoskeleton, Nuclear
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Ovarian function
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Expression regulated by
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Ovarian localization
Oocyte
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Re-localization of nuclear DNA helicase II during the growth period of bovine oocytes Baran V, et al .
Nuclear DNA helicase II (NDH II) is the bovine homolog of human RNA helicase A. The aim of this study was to compare NDH II localization between somatic cells (bovine embryonal fibroblasts) and female germ cells (oocytes), with the main focus on the dynamic changes in the redistribution of NDH II during the growth phase of the bovine oocytes. The fine granular staining of NDH II was spread in the whole nucleoplasm of fibroblasts, excluding the reticulated nucleoli. In contrast, the large reticulated nucleoli of the growing oocytes isolated from early antral follicles exhibited strong positivity for NDH II together with the immunostaining signals of upstream binding factor (UBF) and RNA polymerase I subunit (PAF53), documenting the high synthetic activity of these nucleoli. At the time of termination of oocyte growth, NDH II was preferentially located at the nucleolar periphery together with proteins of fibrillar centres. In fully grown oocytes, NDH II was still present in the thin periphery shell around the compact nucleolar core. The semiquantitative RT-PCR revealed that the average signal of NDH II mRNA in fully grown oocytes was only at 40% level in comparison with growing oocytes. Western blot analysis further confirmed that a 140 kD NDH II protein was abundant in growing oocytes, while the signal was substantially weaker in fully grown oocytes. The significant decrease in NDH II gene expression and in NDH II mRNA translation correlates with a termination of the oocyte growth. Altogether, the results demonstrate that NDH II expression parallels the activity of ribosomal RNA biosynthesis in the bovine growing oocytes.