Structure of the Xenopus laevis TFF-gene xP4.1, differentially expressed to its duplicated homolog xP4.2

TFF-peptides (formerly P-domain peptides, trefoil factors) represent major secretory products of mucous epithelia in mammals and amphibia. The nucleot ide sequence of a large portion of a gene encoding the TEE-peptide xP4.1 fr om Xenopus laevis and its genomic organization were determined in the prese nt study. The peptide xP4.1 containing four TEE-domains is thought to repre sent the functional frog homolog of human TFF2 (formerly hSP). The xP4.1 ge ne analyzed spans a region of about 7 kb and consists of six exons. Each TE E-domain is encoded by a single exon flanked by type 1 introns typical of s huffled modules. The 5'-upstream region contains a TATA-box, and potential binding sites for hepatocyte nuclear factor 3 and AP-1. Furthermore, the cD NA sequence of a transcript named xP4.2 with 91% similarity to xP4.1 is pre sented. RT-PCR analysis revealed that xP4.1 and xP4.2 genes are differentia lly expressed. xP4.1 transcripts are detectable only in the stomach, but no t in the esophagus, whereas xP4.2 transcripts are found both in the esophag us and in the stomach with a descending gradient from fundus to antrum. (C) 1999 Elsevier Science B.V. All rights reserved.