Herrin D L, Schmidt G W
Botany Department, University of Georgia, Athens 30602.
J Biol Chem. 1988 Oct 15;263(29):14601-4.
Photosystem I-deficient Chlamydomonas reinhardtii mutants M18 and F27 lack mature mRNA for the psaA1 gene of photosystem I but accumulate unspliced and partially spliced psaA1 transcripts. Analysis of these transcripts indicate that 1) exon 1 of psaA1 is transcribed separately from exon 2, 2) exon 2 is cotranscribed with the psbD gene, and 3) at least two nuclear gene products are required for exon 1-exon 2 trans-splicing. In addition, analysis of chloroplast transcription in permeabilized cells shows that exon 3 is near the 5' end of a separate transcription unit, indicating that exon 2-exon 3 ligation also occurs by a trans-splicing mechanism.
缺乏光系统I的莱茵衣藻突变体M18和F27没有光系统I的psaA1基因的成熟mRNA，但积累了未剪接和部分剪接的psaA1转录本。对这些转录本的分析表明：1）psaA1的外显子1与外显子2分开转录；2）外显子2与psbD基因共转录；3）外显子1-外显子2的反式剪接至少需要两种核基因产物。此外，对透化细胞中叶绿体转录的分析表明，外显子3靠近一个单独转录单元的5'端，这表明外显子2-外显子3的连接也是通过反式剪接机制发生的。
