WAC, a novel WW domain-containing adapter with a coiled-coil region, is colocalized with splicing factor SC35.

WW domains mediate protein-protein interactions in many intracellular processes. In pre-mRNA splicing, WW domains participate in cross-intron bridging. These WW domains are characterized by a central aromatic block of three tyrosine residues. We identified a novel protein containing the same type of WW domain. The gene encoding the protein, named WAC, is located in human chromosome 10p11.2-10p12.1. A Drosophila melanogaster WAC homolog (CG8949) was identified as a Rosetta stone protein. Domain fusion analysis of the Rosetta stone protein linked WAC to splicing factor SNRP70. WAC existed mainly in a tyrosine-phosphorylated form. Immunofluorescence analysis colocalized WAC with SC35, the marker for pre-mRNA splicing machinery. Our analysis suggests that WAC represents a novel member of WW-domain-containing proteins for RNA processing.