Sequence motifs shared by the 5' flanking regions of two epidermis-specific genes in the ascidian embryo

HrEpiA, B, C and D are epidermis-specific genes of the ascidian embryo, which show different temporal expression patterns during embryogenesis. In this study we investigated the putative cis-regulatory elements shared by HrEpiB and HrEpiD. Fusion genes were constructed by ligating the 5' upstream regions of the genes with bacterial lacZ. Microinjection of the constructs into fertilized eggs revealed that the 5' flanking region from -345 to + 200 of HrEpiB, regarding the transcription initiation site as +1, was sufficient for the epidermis-specific expression of lacZ, and that from -166 to +108 of HrEpiD was also sufficient for the epidermis-specific expression of the reporter gene. A comparison of the sequences of these two regions demonstrated several conserved sequences for DNA-binding regulatory proteins; some were shared by both genes and some were exclusive to each. In addition, the 5' flanking regions of the genes shared several sequence motifs. These common and uncommon sequences may be responsible for their proper spatial and temporal expression during the differentiation of epidermal cells of the ascidian embryo.