GATA-TYPE ZINC-FINGER MOTIF-CONTAINING SEQUENCES AND CHORION GENE-TRANSCRIPTION FACTORS OF THE SILKWORM BOMBYX-MORI

To characterize a DNA-binding protein, BCFI, which regulates the expre ssion of silkmoth chorion genes through binding to gene promoter eleme nts identical to those recognized by the GATA family of transcription factors, we have carried out polymerase chain reaction amplifications of Bombyx mori genomic DNA using degenerate primers derived from the c onserved DNA binding domain of mammalian GATA factors. Two single copy genes, BmGATA alpha and BmGATA beta, were identified, which encode se quences containing GATA-type zinc finger motifs. The BmGATA beta gene is expressed in follicular and Bm5 tissue culture cells, the two cell types that contain BCFI. No BmGATA alpha gene transcripts were detecta ble in the tissues that were tested. Upon overexpression in Escherichi a coli, a peptide encompassing the BmGATA beta zinc finger motif was a ble to bind specifically to the BCFI recognition motif of the chorion gene promoters. A polyclonal antibody directed against the zinc finger domain of BmGATA beta was also used in gel retardation assays to conf irm that factor BCFI is indeed encoded by the BmGATA beta gene. Concep tual translation of a complete cDNA clone encoding the BmGATA beta pro tein revealed that this protein has a size similar to that of an immun oreactive protein, presumably BCFI, which is present in follicular cel l extracts.