Intronic U50 small-nucleolar-RNA (snoRNA) host gene of no protein-coding potential is mapped at the chromosome breakpoint t(3;6)(q27;q15) of human B-cell lymphoma

Background: In eukaryotic cells, nucleolar processing of preribosomal RNAs (prerRNAs) is assisted by a large number of small nucleolar RNAs (snoRNAs) that function in the 2'-O-methylation or the pseudouridylation of rRNAs. Most snoRNAs so far characterized are encoded and processed from introns of premRNAs. Results: We found a novel intronic snoRNA gene, named U50HG, located on chromosome 6q15, at the breakpoint of chromosomal translocation t(3;6)(q27;q15). The U50HG gene is composed of six exons, whose spliced transcripts have little potential for coding a protein, and its introns produce both U50 and U50-like (U50') snoRNAs that are localized in nucleoli. It possesses an oligopyrimidine tract that is characteristic of the 5'-terminal oligopyrimidine (5'TOP) class of genes which have been shown to be coordinately regulated in response to cell growth. Conclusions: U50HG is a member of the nonprotein-coding multiple snoRNA host gene family, as well as of the 5'TOP gene family similar to UHG (U22 host gene), U17HG (U17 host gene), U19HG (U19 host gene) and gas5 (growth arrest-specific transcript 5 gene). It is novel to find that the snoRNA gene is located at the breakpoint of chromosomal translocation t(3;6)(q27;q15) involved in human B-cell lymphoma.