We have isolated a novel human cDNA with a predicted amino acid sequence homologous to GCN5, a protein considered to be a regulator of transcriptional activation in yeast. This cDNA, termed GCN5L1 (GCN5-like 1), consists of 545 nucleotides including an open reading frame of 378 bp that encodes a 126-amino-acid peptide having 23.5% identity to yeast GCN5. Northern-blot analysis revealed transcription of this gene in all human tissues examined. We isolated a genomic clone corresponding to this cDNA from a human cosmid library and mapped it to chromosome 12q13 --> q14 by fluorescent in situ hybridization (FISH).