PHAX
Description
The PHAX (phosphorylated adaptor for RNA export) is a protein-coding gene located on chromosome 5.
Phosphorylated adapter RNA export protein is a protein that in humans is encoded by the PHAX gene.
PHAX, also known as RNA U small nuclear RNA export adapter protein, is a phosphoprotein adapter involved in the XPO1-mediated export of U snRNA from the nucleus. It acts as a bridge between the cap binding complex (CBC)-bound snRNA and the GTPase Ran in its active GTP-bound form, along with the export receptor XPO1, which are essential components for U snRNA export. Phosphorylation of PHAX in the nucleus is required for the assembly and export of the U snRNA export complex. Conversely, its dephosphorylation in the cytoplasm leads to the disassembly of the export complex. PHAX is then recycled back to the nucleus via the importin alpha/beta heterodimeric import receptor. The directionality of nuclear export is thought to be governed by the asymmetric distribution of the GTP- and GDP-bound forms of Ran between the cytoplasm and the nucleus. PHAX's compartmentalized phosphorylation cycle also contributes to this directionality. PHAX binds strongly to m7G-capped U1 and U5 small nuclear RNAs (snRNAs) in a sequence-unspecific and phosphorylation-independent manner. It also plays a role in the biogenesis of U3 small nucleolar RNA (snoRNA), facilitating its transport from the nucleoplasm to Cajal bodies. PHAX binds strongly to m7G-capped U3, U8, and U13 precursor snoRNAs and weakly to trimethylated (TMG)-capped U3, U8, and U13 snoRNAs. It also binds to telomerase RNA. PHAX is found in a U snRNA export complex with PHAX/RNUXA, NCBP1/CBP80, NCBP2/CBP20, RAN, XPO1, and m7G-capped RNA. It is also part of a precomplex with PHAX/RNUXA, NCBP1/CBP80, NCBP2/CBP20, and m7G-capped RNA. PHAX interacts with NCBP1/CBP80 and is found in a complex with snoRNA. It also interacts with NCBP2/CBP20.
PHAX is also known as RNUXA.
Associated Diseases
- adult-onset autosomal dominant demyelinating leukodystrophy
- Hirschsprung disease
- nonpapillary renal cell carcinoma
- colorectal cancer
- cancer
- Alzheimer disease
- type 1 diabetes mellitus
- Huntington disease
