Human placental protein 14 gene: sequence and characterization of a short duplication

Differential hybridization of cDNAs corresponding to mRNAs expressed in the human endometrium during the secretory phase or during the first trimester of pregnancy, but not during the proliferative phase, allowed us to isolate and characterize cDNAs encoding human placental protein 14 (PP14). The cDNA was used to isolate the PP14 gene from a human genomic library. The entire gene encompasses 5.05 kb divided into seven exons by six introns. The human PP14 gene shows identical organization with the ovine beta-lactoglobulin gene, as expected from protein homology. Sequencing of 3 kb of the 5'-flanking region of the gene allowed us to characterize a 400-bp duplication of the PP14 gene lying at position -2,660. This duplication was homologous to 100 bp of exon 4 and 300 bp of intron 4, including 180 bp corresponding exactly to the right arm of an Alu element lying on the complementary strand. This homology suggests that this duplication may have arisen through a retroposition event.