Upstream ORF-Encoded ASDURF Is a Novel Prefoldin-like Subunit of the PAQosome

The PAQosome is an 11-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 12th subunit of the PAQosome. ASDURF displays
significant structural homology to β-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 provide
an example of a 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.