PRT1, AN UNUSUAL RETROTRANSPOSON-LIKE SEQUENCE IN THE FUNGUS PHYCOMYCES-BLAKESLEEANUS

This work reports the isolation and structural characterization of Prt 1, a 4.7 kb retrotransposon-like sequence from the filamentous fungus Phycomyces blakesleeanus. Two open reading frames are found within Prt 1. The first shows no similarity with known genes. The second encodes peptide stretches similar to the reverse transcriptase and RNaseH doma ins of the Ty3/gypsy family of LTR-retrotransposons. Prt1 lacks long t erminal repeats, having instead short (54 bp) terminal inverted repeat s. No target site duplication has been found. A single copy of Prt1 wa s detected in the genome of P. blakesleeanus. Adjacent to this sole co py of PI tl, a cluster of various short sequence repeats, both direct and inverted, is found. These sequences, which are reminiscent of defe ctive, non-retroviral transposable elements, are also represented in o ther regions of the P. blakesleeanus genome.