Occurrence of a copia-like transposable element in one of the introns of the potato starch phosphorylase gene

✍ Scribed by Camirand, Anne ;St-Pierre, Benoit ;Marineau, Claude ;Brisson, Normand

• Publisher: Springer
• Year: 1990
• Tongue: English
• Weight: 822 KB
• Volume: 224
• Category: Article
• ISSN: 0026-8925
• DOI: 10.1007/bf00259448

✦ Synopsis

The gene coding for starch phosphorylase (EC 2.4.1.1) was isolated from a potato genomic library constructed in lambda EMBL3. It is an unusually long plant gene (16.4 kb) which encodes a preprotein of 966 amino acids. The phosphorylase coding sequence is interrupted by 14 introns whose positions do not match those of the introns in the human glycogen phosphorylase gene. A 78 amino acid central peptide unique to plant plastidial phosphorylases is hypothesized to have arisen through the mis-splicing of an intron-exon junction site in an ancestral gene. The fifth intron of the phosphorylase is very large (approximately 7 kb) and contains a copia-like transposable element inserted in the opposite orientation to that of the phosphorylase gene. This element has been named Tst1; it is bordered on the 5' and 3' sides by long terminal repeats of 285 and 283 bp respectively, which define an internal domain of 4492 bp. Tst1 contains 4 open reading frames (ORFs) that encode protein domains for a reverse transcriptase, an integrase, an RNA-binding site and a protease. Transcription of the phosphorylase gene appears to proceed unimpaired through the copia element.