FIG. 2.

TATA box mutagenesis in the Δ42 allele results in growth defects and aberrant start site selection. Lower-case sequences indicate mutations in the wild-type TATA box. (A) Fivefold dilutions of representative mutants to assign growth values. 1X equals an optical density at 600 nm of 0.25. (B) Primer extension of transcripts produced by TATA box mutant alleles using primers complementary to U6 and U4 RNAs. Cells were grown under selection for the plasmids containing the mutant SNR6 allele and the pseudo-wild-type U6 allele prior to isolation of whole-cell RNA. U6 +1 indicates the U6 RNA that has initiated at the normal start site. U6 +5 indicates an aberrant start site 4 nucleotides downstream. ψ-wt U6 is pseudo-wild-type U6 RNA and is 13 nucleotides shorter than wild-type U6. U4 RNA is used as a normalization standard in this experiment.