Reporter Plasmids Used for the Transcriptional Analysis of the X. laevis Vitellogenin (VitB1) Promoter in Yeast pVitB1-CYC1 contains 554 nucleotides of vitellogenin B1 promoter sequences including all control elements, except the TATA box, fused to the minimal yeast CYC1 promoter in pLGΔSmaI-XhoI (see Fig. 1). In pLGΔVitB1, 193 nucleotides of promoter-proximal sequences including the CTF/NF1 binding site (CTF) were deleted, locating the vitellogenin B1 upstream promoter sequences (−596 to −235) close to the CYC1 TATA box in pLGΔSmaI-XhoI. pVitB1-DED1 is a derivative of pVitB1-CYC1, in which the CYC1 promoter is replaced by the minimal yeast DED1 promoter. Positions of the EREs (ERE and ERU) and the CTF/NF1-specific DNA element (CTF) are indicated. Numbers correspond to vitellogenin B1 promoter sequences upstream from the site of transcription initiation. Numbers in parentheses above the pLGΔVitB1 diagram correspond to original vitellogenin B1 promoter sequences before the deletion. Arrows show the orientation of transcription from the reporter gene, lacZ.