pCal, a highly unusual Ty1/copia retrotransposon from the pathogenic yeast Candida albicans.
Retrotransposons are mobile genetic elements. They can transpose via the reverse transcription of mRNA into double-stranded DNA (dsDNA) followed by the insertion of this dsDNA into new sites within the host genome. The unintegrated, linear, dsDNA form of retrotransposons is usually very rare. We report here the isolation of a retrotransposon from Candida albicans which is unusual in this respect. This element, which we have named pCal, was first identified as a distinct band when uncut C. albicans DNA was examined on an agarose gel. Sequence analysis of the cloned element revealed that it is a retrotransposon belonging to the Ty1/copia group. It is estimated that pCal produces 50 to 100 free, linear, dsDNA copies of itself per cell. This is a much higher level of expression than even that of the system in which Ty1 is expressed behind the highly active GAL1 promoter on a high-copy-number plasmid (about 10 copies per cell). Another unusual feature of pCal is that its Pol enzymes are likely to be expressed via the pseudoknot-assisted suppression of an upstream, in-phase stop codon, as has been shown for Moloney murine leukemia virus.
Matthews
G D
GD
Department of Biochemistry, University of Otago, Dunedin, New Zealand.
Goodwin
T J
TJ
Butler
M I
MI
Berryman
T A
TA
Poulter
R T
RT
D000595:Amino Acid Sequence; D001483:Base Sequence; D002176:Candida albicans / Q000235:genetics*; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D018388:Codon, Terminator; D004251:DNA Transposable Elements / Q000235:genetics*; D004271:DNA, Fungal / Q000032:analysis / Q000235:genetics / Q000302:isolation & purification; D010450:Endopeptidases / Q000235:genetics; D015966:Gene Expression Regulation, Fungal; D015684:Gene Products, pol / Q000235:genetics / Q000378:metabolism; D019426:Integrases / Q000235:genetics; D008969:Molecular Sequence Data; D015394:Molecular Structure; D016366:Open Reading Frames; D010802:Phylogeny; D010957:Plasmids; D011401:Promoter Regions, Genetic; D012194:RNA-Directed DNA Polymerase / Q000235:genetics; D018626:Retroelements; D012260:Ribonucleases / Q000235:genetics; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
D018388:Codon, Terminator; D004251:DNA Transposable Elements; D004271:DNA, Fungal; D015684:Gene Products, pol; D018626:Retroelements; D019426:Integrases; D012194:RNA-Directed DNA Polymerase; D012260:Ribonucleases; D010450:Endopeptidases