Primer extension analysis of the start site for transcription of sspG and yurS. RNA from cells of strain IB464 was isolated 7.5 h into sporulation, and the primer extension product was obtained and analyzed as described in Materials and Methods. The primer used is yurS-140, which anneals only to yurS. Lanes a, g, c, and t are DNA sequencing reactions with the same primer and plasmid pIB517; lane 1 is a primer extension reaction with sporulating-cell RNA. The primer extension product is marked with an arrow, and the transcription start site on the sspG upstream sequence to the left of the figure is marked with a square. Note that the sequence shown is the complement of the mRNA sequence.