COMMON CIS-ACTING ELEMENTS CRITICAL FOR THE EXPRESSION OF SEVERAL GENES OF TOXOPLASMA-GONDII

Transient transformation of Toxoplasma using the CAT (chloramphenicol acetyl transferase) reporter gene has been used to map promoter elemen ts of four genes encoding dense granule proteins (GRA1, GRA2, GRA5 and GRA6), Intense CAT activities (GRA1 > GRA5 > GRA2 > GRA6) are detecte d for constructs containing 379 bp, 276 bp, 209 bp and 265 bp upstream of the transcription start site of the GRA1, GRA2, GRA5 and GRA6 gene s, respectively, Deletion analysis shows that optimal promoter activit y of each gene is contained in the proximal region of the transcriptio n start site: -129 to -47 for GRA1, -87 to -37 for GRA2, -156 to -30 f or GRA5 and -146 to -27 for GRA6. Quantitative CAT assay and mutation analysis show that repeated motifs (A/TGAGACG) found in either orienta tion with respect to transcription are critical elements of these defi ned promoter regions. We have found such sequence elements in the upst ream region of other Toxoplasma genes such as Tub1 and within the stre tch of 27 bp repeats of the SAG1 promoter.