Fig. 1. (A) Two major classes of Xag1 transcripts are detected by 5' RACE. One class initiates downstream of a TATA box (+1; black arrow). The second class consists of several transcripts that initiate 150-100 bp upstream of the TATA box (gray arrows). (B) Northern blot analysis of RNA isolated from blastula through tailbud (stage 9-30) embryos shows the first class of transcript is the most abundant in the embryo. Both probes recognize in vitro transcribed Xag1 upstream sequence (not shown). (C) Sequence of the Xag1 genomic region used in this study. 3 Ets-like binding sites (EBS; dark-gray boxes), an ATF/CREB-like binding site (CRE, light-gray box) and the TATA box (unshaded box) are indicated. The black arrow indicates the initiation site of the major transcript, the gray arrow indicates the 5' limit of the rarer transcripts that were isolated. Also shown are the 14 bp regions (1-7) and the 4 bp region 8 that were replaced in the linkerscan analysis (see Fig. 3).

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