RESULTS
The complete sequence of the Tetrahymena H3 gene family
We have determined the sequence of three Tetrahymena
thermophila histone H3 genes (Fig. 2). All of the bands detected
by a yeast H3 probe on a Southern blot of macronuclear DNA
(20) can be accounted for by the restriction maps of these clones
(Fig. 1); thus we have cloned the entire complement of
T. thermophila H3 genes.
HHTl and HHT2 encode the major H3 protein, a 135 amino
acid protein that is identical to the major H3 of Tetrahymena
pyriformis (14) and 87% identical to the major animal H3
(Fig. 3). The DNA sequence of HHT2 is 93% identical to HHTl
over the coding region. The genes contain 3 and 4 TAA codons,
which encode glutamine in Tetrahymena (20), respectively;
neither gene contains an intron.