Display of different modes of transcription by the promoters of an early embryonic gene, Zfp352, in preimplantation embryos and in somatic cells.

We have previously reported a Krupple-like finger protein gene, Zfp352, which is expressed temporarily in two- to eight-cell mouse embryos. The Zfp352 gene is intron-less in the coding region but carries a solitary 4.3-kb intron in the 5'-untranslated region. In this study, we have analyzed the Zfp352 promoter activity in early embryos and in somatic cells. We determined that the major Zfp352 promoter, designated P1 and located upstream of exon 1, is utilized in both early embryos and in somatic cells. A TATA-like box and a transcription initiator element are discernible in the P1 promoter. We uncovered an alternative promoter, designated P2, in the intron. 5'-Rapid amplification of cDNA ends and real-time RT-PCR experiments indicated that the P2 promoter is weak and is probably fortuitous in early embryos. In somatic cells, however, transfection experiments showed that P2 is as active as P1 as a promoter. Furthermore, P2 appears to be composed of two different subdomains used differentially for transcription initiation in embryos and in somatic cells. Our observations may bear relevance in explaining developmental deficiencies associated with somatic cell cloning experiments.