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 rap idly degraded. The stable RNA products from this locus are actually en coded within eight different introns of the UHG preRNA. These small nu cleolar RNAs (snoRNAs) assemble into ribonucleoproteins, some of which have been shown to function in rRNA processing and modification. In o rder to more fully characterize the locus, we have mapped UHG to chrom osome 11q13 by fluorescence in situ hybridization (FISH). Radiation hy brid mapping placed this sequence-tagged site with very high probabili ty (led >19) to chromosome II, approximately 10.1 cR distal to framewo rk marker WI-8652. We also investigated the possibility that the expre ssion of UHG was subject to genomic imprinting. Several laboratories h ave shown that non-protein-coding mRNAs are frequently associated with imprinted domains in mammalian cells. We used a novel somatic cell hy brid method to assay parent-of-origin effects in the expression of UHG alleles and found that, unlike XIST, IPW, and H19, this RNA is expres sed biparentally. Additional FISH experiments using anti-U22 oligonucl eotides revealed that, as with U3, this snoRNA is localized throughout the nucleolus.