Alternative titles; symbolsRNA, U SMALL NUCLEAR, EXPORT ADAPTOR; RNUXAHGNC Approved Gene Symbol: PHAXCytogenetic location: 5q23.2 Genomic coordinates (GRCh38...
Alternative titles; symbols
HGNC Approved Gene Symbol: PHAX
Cytogenetic location: 5q23.2 Genomic coordinates (GRCh38): 5:126,600,946-126,627,251 (from NCBI)
PHAX, together with nuclear cap-binding complex (see NCBP1; 600469), the export receptor CRM1 (XPO1; 602559), and RanGTP (see RANGAP1; 602362), is necessary for export of U small nuclear RNA (snRNA) precursors from the nucleus, which in turn is required for assembly of spliceosomal U small nuclear ribonucleoprotein particles (snRNPs) (Ohno et al., 2000).
▼ Cloning and Expression
In mouse, Ohno et al. (2000) identified Phax (phosphorylated adaptor for RNA export) as the additional factor required for U snRNA export complex assembly in vitro. In vivo, Phax is required for U snRNA export but not for Crm1-mediated export in general. Phax is phosphorylated in the nucleus and then exported with RNA to the cytoplasm, where it is dephosphorylated. Phax phosphorylation is essential for export complex assembly, while its dephosphorylation causes export complex disassembly. The compartmentalized Phax phosphorylation cycle can contribute to the directionality of export. Several human ESTs share more than 90% homology with the mouse Phax gene, indicating that a homologous PHAX gene exists in the human genome.