The cDNA sequence and expression of an ubiquitin-tail gene fusion in Neurospora crassa

The genome of Neurospora crassa contains at least one natural fusion gene encoding a single ubiquitin (UBI) unit with a 78-amino acid C-terminal extension. The predominantly basic tail sequence corresponds to a highly conserved ribosomal protein identified in other organisms. The 0.7-kb UBI fusion transcript is mainly expressed in germinating conidia and other stages of active cell replication. Under starvation conditions attained by nutrient depletion, or after polyamine depletion, the UBI fusion gene is shut off while the polyUBI transcript is preserved. Cycloheximide addition promotes polyUBI, but not UBI fusion transcript accumulation in N. crassa.