Structure and inheritance of sense and anti-sense transcripts from a transposon in the green alga Chlamydomonas reinhardtii.
We have studied the transcription pattern of a 5700 base-pair transposon (TOC1) in Chlamydomonas reinhardtii. Northern blotting and nuclease S1 protection experiments define three classes of major TOC1 RNAs that accumulate to different levels in a number of strains and segregate independently in the progeny of crosses: class 1 RNAs are unstable near full-length sense transcripts whose 5' end maps to the left 217 base-pair repeat of TOC1, class 2 and class 3 RNAs are large, discrete chimaeric transcripts containing full-length sense (class 2) and anti-sense (class 3) copies of TOC1. Sequence motifs common to the 5' non-transcribed regions of C. reinhardtii genes were found upstream from the putative initiation site of class 1 transcripts. A functional polyadenylation site was located in the far-right 237 base-pair repeat of TOC1. Class 1 TOC1 transcripts are initiated, and probably terminated, within the terminal repeats of TOC1 and may represent retrotransposition intermediates. Class 2 and 3 TOC1 transcripts co-segregate with specific TOC1 elements identified on Southern blots. The loci that control the production of high levels of class 1 transcripts could correspond to specific TOC1 elements, i.e. only a few TOC1 elements are transcribed, or to a regulatory locus. The accumulation of an 11,500 to 12,000 base sense transcript (class 2) is reduced two- to fourfold by the presence of a 9500 to 9700 base antisense transcript (class 3). In contrast, the accumulation of the 5' ends of class 1 transcripts are unaffected by the anti-sense TOC1 transcript.
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Department of Molecular and Plant Biology, University of Geneva, Switzerland.
Rochaix
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JD
D001483:Base Sequence; D015152:Blotting, Northern; D015139:Blotting, Southern; D002696:Chlamydomonas / Q000235:genetics*; D003001:Cloning, Molecular; D004247:DNA; D004251:DNA Transposable Elements; D008969:Molecular Sequence Data; D012313:RNA / Q000235:genetics; D016372:RNA, Antisense / Q000235:genetics*; D015183:Restriction Mapping; D015719:Single-Strand Specific DNA and RNA Endonucleases; D014158:Transcription, Genetic
D004251:DNA Transposable Elements; D016372:RNA, Antisense; D012313:RNA; D004247:DNA; D015719:Single-Strand Specific DNA and RNA Endonucleases