THE SAPA PROMOTER FROM STREPTOMYCES-COELICOLOR REQUIRES ACTIVATION SITES AND INITIATOR-LIKE SEQUENCES BUT NOT -10 OR -35 SEQUENCES

The Streptomyces coelicolor sapA gene encodes a spore coat protein. The sapA promoter is regulated developmentally, with maximal expression occurring in aerial hyphae at a late stage of colonial development. The DNA sequences upstream from the transcription start point do not appear to fall into a previously described promoter class, One (or more) putative activation site, required for full activity, is eliminated when 5' deletions extend to between -178 and -72 bases upstream from the transcription start point. In addition, a downstream activation site is destroyed by removing sequences between positions +40 and +120, relative to the transcription start point, in the absence of an intact upstream region, However, temporal regulation of transcription initiation over the course of the life cycle is maintained faithfully in the absence of these elements, even in the smallest 18-bp sapAp fragment containing sequences from positions -8 to +10, Site-specific mutations around the transcriptional start points shift the timing of sapA expression to an earlier stage in the developmental cycle, These results suggest that a novel mechanism may be involved in Streptomyces late gene expression.