Fig. 4.

A. Northern blot probing for crRNAs transcribed from spacer 29 of locus D of S. solfataricus P2. The transformant which apparently lacks CRISPR loci A to D (Table 1) was probed. The vector construct carried the ATV618 gene with a matching protospacer and CC motif. Samples were tested without and with arabinose stimulation of ATV618 mRNA transcription to test whether there was any effect of the mRNA. pEXA2 denotes transformants carrying the empty vector with no insert. Normally processed crRNAs are only visible for transformants carrying the empty vector.

B. Northern blot probing for the protospacer region of ATV145 transcripts from forward and reverse strands. + denotes the total RNA isolated from the pEXA2-ATV145 transformant and − indicates the total RNA isolated from the transformant of the construct pEXA2-ATV145 for which the araS promoter had been exchanged with an archaeal transcriptional terminator (see main text). ‘P’ represents a positive control where a 10 pmol 22-nt-long DNA oligonucleotide is employed that is complementary to the probe. Sequences of oligonucleotide probes are given in Experimental procedures.