EXPRESSION OF HETEROLOGOUS GENES IN SCHIZOPHYLLUM-COMMUNE IS OFTEN HAMPERED BY THE FORMATION OF TRUNCATED TRANSCRIPTS

GPD regulatory sequences were used to express a phleomycin resistance gene (Sh ble) in Schizophyllum commune, resulting in high numbers of p hleomycin-resistant transformants. Attempts to express heterologous ge nes coding for hygromycin B phosphotransferase (hph), aminoglycoside p hosphotransferase (apt), beta-glucuronidase (uidA) and beta-galactosid ase (lacZ) using the same regulatory sequences were not successful and no mRNA could be detected. Cloning the hph and uidA genes in an inter nally deleted GPD gene resulted in truncated transcripts which ended w ithin the 5'-parts of the heterologous genes. Cloning of the same gene s as transcriptional fusions downstream from the Sh ble gene also resu lted in truncated transcripts ending in the 5'-parts of these heterolo gous genes. It is suggested that AT-rich sequences in heterologous gen es might be involved in generating these truncated transcripts, thereb y preventing expression in S. commune.