Cloning and characterization of a novel histone acetyltransferase homologue from the protozoan parasite Toxoplasma gondii reveals a distinct GCN5 family member

In an effort to identify gene products involved in transcriptional regulati on in apicomplexan parasites, the Toxoplasma gondii expressed sequence tag (EST) database was examined for sequences containing similarity to known tr anscriptional components. One EST (dbEST ID #466792) exhibited strong simil arity to yeast GCN5 and other histone acetyltransferases (HATs). Primers we re designed based on the EST sequence and used to amplify an 850 bp fragmen t (containing an intron) from T. gondii genomic DNA which was used to ident ify four cDNA clones from a tachyzoite cDNA library. The complete open read ing frame (ORF) of 3.5 kb was elucidated using 5' RACE and genomic sequence . The deduced amino acid sequence of the coding region shows that the C-ter minal domain possesses unequivocal similarity to GCN5 family members. Howev er, unlike other lower eukaryotes, T. gondii GCN5 has an extended N-termina l domain similar in length, but not in composition, to metazoan HAT protein s. These features distinguish T. gondii GCN5 as a novel member of the GCN5 family. A portion of the cDNA sequence was used as a probe to isolate three overlapping clones from a T. gondii genomic library, generating a similar to 7.5 kb map of the GCN5 locus which contains seven exons separated by six introns. Southern analysis verifies the predicted map and suggests that a similar locus may be present elsewhere in the genome. (C) 2000 Elsevier Sci ence B.V. All rights reserved.