Analysis of the promoter region of human placenta-specific DSCR4 gene

The gene DSCR4 locates in the band q22.2 of human chromosome 21 and encodes a protein of 118 amino acids. Expression of DSCR4 is restricted to human placenta and placental choriocarcinoma cell lines BeWo and JEG3. The 5′-RACE method using RNA from human placenta indicated the major transcription start site at 93 nt upstream (nt − 93) of the initiation codon. Transfection assay using a series of deletion constructs of the 5′-flanking region fused to the luciferase reporter gene identified three positive regions nt − 2200 to − 2088, nt − 2064 to − 1924, nt − 810 to − 632 and two negative regions nt − 1923 to − 1740, nt − 631 to − 425. The computer analysis predicted the presence of several cis-elements in these regions and the promoter assay using various mutants of consensus sequence identified two distinct cis-elements for OLF-1 and E47. The electrophoretic mobility shift assay (EMSA) using the extracts of DSCR4-expressing cells confirmed the binding of certain protein factors to these cis-elements. In fact, OLF-1-like transcription factor, EBF-3 and EBF-4 were detected in the DSCR4-expressing cell lines and human placenta. Based on these data, we postulated that transcription of DSCR4 gene is regulated positively by binding of OLF-1-like transcription factor and negatively by binding of E47-like transcription factor.