We have determined the nucleotide sequence of a segment of chromosome III contained in the right part of the lambda PM3270 clone, for a total of 8824 bp. This sequence contains an unusual long open reading frame, YCR601, of 6501 bp that encodes for a protein of 2167 amino acids that show no homology with other known proteins. YCR601 was disrupted by internal deletion and insertion of LEU2 gene and is a non-essential gene, however, it is transcribed during vegetative growth yielding a polyadenylated mRNA of approximately 7 kb.