FIG. 1.

gas5 is a multi-snoRNA host gene. (a) Black boxes represent the 12 exons of mouse gas5; cross-hatched boxes represent the snoRNA sequences present within nine of its introns. Numbers above and below the gene are the lengths of exons and introns, respectively. The alternative splicing event that results in the inclusion of the seventh exon is indicated. (b) Northern analyses were performed on mouse total RNA (T) and RNA isolated by immunoprecipitation with anti-fb (αfb) antibodies by using probes derived from intronic sequences of gas5. (The same blot was probed for U75 and U79, indicating that the less-efficient immunoprecipitation of U75 is not due to underloading of the lane.) Each intron except the fourth and seventh produces a stable RNA species between 60 and 90 nucleotides long. The nine mouse gas5 anti-fb immunoprecipitable RNAs are named U74, U75, U76, U44, U78, U79, U80, U47, and U81. The human gas5 gene encodes, in addition to the nine murine snoRNAs, a tenth snoRNA (U77) within intron 4 (data not shown). The sizes of the human exons, in order, are 30, 53, 36, 40, 30, 38, 77 or 38 (alternatively spliced), 54, 30, 23, 48, and 210 nucleotides and introns are 916, 194, 191, 321, 281, 307, 188, 523, 167, 179, and 205 nucleotides.