PROMOTER UTILIZATION IN A MOSQUITO RIBOSOMAL DNA CISTRON

In the mosquito Aedes albopictus, two potential RNA polymerase I promo ters that map 531 and 143 nucleotides upstream of the 18S rRNA gene ha ve been defined on the basis of sequence homology with rRNA promoters from other species. Using the polymerase chain reaction, we confirmed that a 717 nucleotide region spanning the upstream (-531) and downstre am (-143) promoters is homogeneous in genomic DNA and in cloned DNA. D NA probes representing each of these promoters, as well as upstream '' spacer'' promoters, exhibited protein-binding activity, and each unlab eled probe was an effective competitor of protein binding with the oth er probes, suggesting that these potential regulatory sequences intera ct with a common protein(s). Analysis of precursor ribosomal RNAs accu mulated during temperature shock indicated that transcription is initi ated primarily at the upstream (-531) promoter. RNAse protection and p rimer extension analyses confirmed the predominant use of this promote r, both in cultured cells and in mosquito life stages. (C) 1995 Wiley- Liss, Inc.