The U22 host gene (UHG): chromosomal localization of UHG and distribution of U22 small nucleolar RNA.

The U22 host gene (UHG) is very unusual because it encodes a spliced, polyadenylated RNA that has little apparent coding capacity and is rapidly degraded. The stable RNA products from this locus are actually encoded within eight different introns of the UHG pre-RNA. These small nucleolar RNAs (snoRNAs) assemble into ribonucleoproteins, some of which have been shown to function in rRNA processing and modification. In order to more fully characterize the locus, we have mapped UHG to chromosome 11q13 by fluorescence in situ hybridization (FISH). Radiation hybrid mapping placed this sequence-tagged site with very high probability (lod >19) to chromosome 11, approximately 10.1 cR distal to framework marker WI-8652. We also investigated the possibility that the expression of UHG was subject to genomic imprinting. Several laboratories have shown that non-protein-coding mRNAs are frequently associated with imprinted domains in mammalian cells. We used a novel somatic cell hybrid method to assay parent-of-origin effects in the expression of UHG alleles and found that, unlike XIST, IPW, and H19, this RNA is expressed biparentally. Additional FISH experiments using anti-U22 oligonucleotides revealed that, as with U3, this sno-RNA is localized throughout the nucleolus.