Upstream ORF-encoded ASDURF is a novel prefoldin-like subunit of the PAQosome

The PAQosome is an eleven-subunit chaperone involved in the biogenesis of several human protein complexes. We show that ASDURF, a recently discovered upstream open reading frame (uORF) in the 5’ UTR of ASNSD1 mRNA, encodes the twelfth subunit of the PAQosome. ASDURF, displays significant structural homology to beta-prefoldins and assembles with the five known subunits of the prefoldin-like module of the PAQosome to form a heterohexameric prefoldin-like complex. A model of the PAQosome prefoldin-like module is presented. The data presented here provides an example of ana eukaryotic uORF-encoded polypeptide whose function is not limited to cis-acting translational regulation of downstream coding sequence and highlights the importance of including alternative ORF products in proteomic studies.