Sequence organization in Dictyostelium: unique structure at the 5'-ends of protein coding genes

We have compared the sequences which lie 5' to the coding regions of 15 Dictyostelium genes transcribed by RNA polymerase II. These sequences are extremely (approximately 90%) A + T rich and contain extensive homopolymeric regions. Like most eukaryotic genes, those in Dictyostelium possess a TATA or Goldberg-Hogness Box approximately 25-35bp 5' to the site of transcription initiation. In addition, each gene contains an oligo (dT) stretch between the TATA Box and mRNA start site; this oligo (dT) sequence is, thus far, unique to Dictyostelium. We suggest that the TATA-oligo (dT) structure is an essential component of the Dictyostelium promoter. The general sequence structure of coding, non-coding and untranscribed flanking regions in Dictyostelium is also discussed.