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. 1997 Nov 11;94(23):12509–12514. doi: 10.1073/pnas.94.23.12509

Figure 1.

Figure 1

(A) Genomic map of mouse Igf2 and upstream transcripts. Igf2 promoters (horizontal arrows): P0, P1, P2, and P3. Ins2; Igf2 exons (black boxes): u1, u2, E1-E6. DNA repeats (shaded boxes): B2, CG-rich. DNase I HS (vertical arrows); ∗, embryo-specific HS. P0 transcript: exons (thick line), introns (thin line) includes exons u1, u2, E4-E6. A 1591-bp PCR product of P0 (primers UP2 and LP1) was cloned and sequenced. P0 poly(A)+ addition sites were not mapped; however, on Northern blots P0 is identical in size to the 5-kb P2 transcript (data not shown). The identical size suggests similar inclusion of E6 sequences downstream of LP1. Transcribed AS regions were named according to the nearest associated poly(A)+ addition sites—a, b, c: Igf2as-a, Igf2as-b, Igf2as-c. Putative transcription start sites, a′, b′, and c′. Open boxes represent sequenced AS RT-PCR products from primer pairs UP5 and LP7: b transcript, UP6 and LP6: c transcript, UP3 and LP9 or UP4 and LP5: a or a′ transcript. We were unable to clone or sequence a fragment from primer pair UP3 and LP5, and therefore cannot propose a final structure for a putative a-a′ AS transcript. Three hundred base pair regions upstream of putative transcription start sites were examined for regulatory sequences using the tfd software program at the Medical Research Council, Human Genome Mapping Project. Only the b′ site was associated with major promoter element motifs. (B) DNA sequence data for upstream transcripts. Nucleotide positions are numbered as per ref. 18. Putative transcription starts (vertical arrows): P0: 8,512; b′: 17,587; c′: 11,943. P0 acceptor splice sites (ASS) and donor splice sites (DSS): u1 putative ASS (underlined): 8,584–8,597; u1 DSS: 8,825–8,832; u2 ASS: 10,120–10,134; u2 DSS: 10,952–10,959. AS transcript splice sites and (underlined) poly (A+) addition signal nucleotide positions numbered for the complementary, upper strand, as follows: b1 DSS: 17,406–17,399; b2 ASS, DSS: 12,932–12,918, 12,862–12,855; b3 ASS, DSS: 12,200–12,186, 11,976–11,969; b4 ASS: 11,273–11,259. Poly(A)+ signals: a: 8,120–8,115; b: 9,651–9,646; c: 9,808–9,803.