Figure 3.

(A) Alignment of predicted amino acid sequences of the E. crassus histone H3 genes with the T. thermophila histone H3 sequences. The sequences of two of the three T. thermophila H3 histones (HHT1, -3) (28) and a histone consensus sequence (22) were aligned with the deduced amino acid sequences of the E. crassus polytene-specific (P) and vegetative (V) H3 histones using the megalign program (DNAstar, Madison, WI). The third Tetrahymena gene, HHT2, encodes a protein that is identical to HHT1. Stars indicate the positions where the two insertions occur in the polytene-specific H3 histone. Positions where the amino acid sequences are identical to the T. thermophila HHT1 sequence are designated as dashes. (B) The DNA sequence of the 5′ noncoding regions of the two histone H3 genes is shown with the start sites of transcription indicated in a larger font. The ATG start codon and end of the telomeric repeats (CCCC) are italicized and underlined. Boldface italics in the H3(V) sequence indicate two 9-bp stretches of sequence identity with sequences surrounding the transcriptional start site of the H4 histone gene described previously (11).