Fig. 5. (A) Gel shift analysis shows a complex formed on the Xag1 promoter at neurula stages. Cell extracts were made from cement gland primordia dissected out of the embryo at stages 15-17 (mid-neurula) and subjected to electromobility shift analysis with labeled Xag1 probe in the presence or absence of cold competitors. Lane1, probe only; lane 2, probe plus extract; lane 3, probe plus extract and Xag1 competitor; lane 4, probe plus extract and EBS competitor; lane 5, probe plus extract and mutated EBS competitor; lane 6, Xag1 probe plus extract and CRE competitor; lane 7, probe plus extract and mutated CRE competitor; lane 8, probe plus extract and OCTA competitor. (B) Sequence of Xag1 probe and cold competitors used.