[en] The cel7A sequence variation was analyzed between the wild type (Lentinula edodes KACC42378) and its cellulase activity enhanced mutant LER277. LER277 was induced by using gamma ray radiation (60Co) at the LD99 dose (0.94 kGy). Cloning and sequencing results showed that the cel7A coding DNA sequence (CDS) of LER277 had fve nucleotide substitutions (T→C, 201, 285 and 744 nt; A→G, 525 nt; C→T, 540 nt) and one hexanucleotide repeat insertion (GGCACC, within 1375-1392 nt) compared to that of the wild type. The Five nucleotide substitutions did not change the deduced amino acids and the hexanucleotide insertion elongated the GT repeat in a serine/threonine/glycine-rich linker. These results suggest that the enhancement of the cellulase activity in LER277 partly stemmed from cel7A changes by which the GT repeat of the linker is elongated