Fox-1 homolog A also known as ataxin 2-binding protein 1 (A2BP1) or hexaribonucleotide-binding protein 1 (HRNBP1) or RNA binding protein, fox-1 homolog (RBFOX1), is a protein that in humans is encoded by the RBFOX1 gene.

Ataxin-2 binding protein 1 has an RNP motif that is highly conserved among RNA-binding proteins. This protein binds to the C-terminus of ataxin-2 and may contribute to the restricted pathology of spinocerebellar ataxia type 2 (SCA2). Ataxin-2 is the gene product of the SCA2 gene which causes familial neurodegenerative diseases. Ataxin-2 binding protein 1 and ataxin-2 are both localized in the trans-Golgi network. Several alternatively spliced transcript variants encoding different isoforms have been found for this gene. Additional transcript variants have been found but their full length nature has not been determined. (provided by RefSeq)
Function: RNA-binding protein that regulates alternative splicing events by binding to 5'-UGCAUGU-3' elements. Regulates alternative splicing of tissue-specific exons and of differentially spliced exons during erythropoiesis.