MOLECULAR-CLONING OF THE RNA-POLYMERASE-I TRANSCRIPTION FACTOR HUBF NOR-90 (UBTF) GENE AND LOCALIZATION TO 17Q21.3 BY FLUORESCENCE IN-SITU HYBRIDIZATION AND RADIATION HYBRID MAPPING/

The 90-kDa nucleolus organizer region autoantigen (NOR-90) was previou sly shown to be identical to human upstream binding factor (hUBF), whi ch has two molecular mass forms of 89 and 93 kDa, respectively. hUBF/N OR-90 is a member of the HMG-box DNA-binding protein family and is kno wn to bind to enhancer regions upstream of the ribosomal RNA genes, wh ich are clustered at NORs. The smaller version of UBF lacks an interna l 111-bp region corresponding to 37 amino acids in the second HMG-box of the larger form. We isolated human genomic clones from a phage libr ary and localized one of them by fluorescence in situ hybridization to chromosome 17q21.3, DNA sequence analysis showed that the Ill-bp regi on represented a single exon, consistent with the previous notion that the two isoforms were products of alternative pre-mRNA splicing of a single gene in human. Radiation hybrid mapping placed this STS with ve ry high probability (LOD > 19) to chromosome 17, approximately 3.77 cR distal to MIT framework marker UTR-9641. The order of the markers (a partial list) from this region was UTR-9641, SGC30031, WI-17308, D17S9 30, NOR53/33, WI-16100, D17S920, WI-16913, and WI-6808. (C) 1997 Acade mic Press.