MULTIPLE CIS-ACTING ELEMENTS ACT COOPERATIVELY IN DIRECTING TROCHOBLAST-SPECIFIC EXPRESSION OF THE ALPHA-TUBULIN-4 GENE IN PATELLA EMBRYOS

During early embryogenesis of the mollusc Patella vulgata the alpha-tu bulin-4 gene is specifically expressed in the differentiation process of a particular cell type, the trochoblasts. The 5' region of the gene has been analysed for elements that are required for the regulation o f the cell-type-specific activation of the gene. In a functional assay , seven elements that play a role in the spatiotemporal activation of the gene were detected in the promoter sequence. They are not required all together at the same time. A core of two elements, together with two or three auxiliary elements, are sufficient in controlling trochob last-specific expression of the gene in the Patella embryo. One of the core elements is always required, without it, the gene is not express ed at all. The other core element acts as a positive element in trocho blasts and as a negative element in non-trochoblasts and thus is invol ved in directing the cell-type specificity of expression. The seven el ements act cooperatively, and at least some of them can substitute for each other. Sequence comparison revealed that six of the seven fragme nts contain the sequence element GTTAA, including one of the core elem ents. Both core elements seem to play a crucial role in the expression of the alpha-tubulin-4 gene during the differentiation process of tro choblasts in the Patella embryo. A model for the regulation of the cel l-type specificity of the gene during trochoblast differentiation is p roposed. (C) 1996 Academic Press, Inc.