Sakamoto W, Chen X, Kindle K L, Stern D B
Boyce Thompson Institute for Plant Research, Cornell University, Ithaca, NY 14853.
Plant J. 1994 Oct;6(4):503-12. doi: 10.1046/j.1365-313x.1994.6040503.x.
Translational control is an important regulatory mechanism in chloroplasts, and is thought to be mediated by cis-acting elements in the 5' untranslated regions (UTRs) of mRNAs. Chloroplast transformation was used to replace the wild-type Chlamydomonas reinhardtii petD 5' UTR with mutated versions. Transformants containing altered 5' UTRs had either a wild-type photosynthetic phenotype, a leaky non-photosynthetic phenotype, or were unable to grow photosynthetically. Among those transformants with a wild-type phenotype were ones containing mutations in a putative Shine-Dalgarno sequence element. The results indicate that two regions of the 362 nucleotide (nt) 5' UTR may act as positive elements for translation, one located between nt 150 and 200, and the other situated approximately 40 nt upstream of the start codon, at nt 320. In every case where translation was compromised, petD mRNA accumulated to a lower level than in wild-type cells, ranging from 15% to 60% in different strains. It was concluded that specific regions of the petD 5' UTR mediate translational activation, and that mRNA stability may be linked to translatability.
翻译控制是叶绿体中的一种重要调控机制，被认为是由mRNA的5'非翻译区（UTR）中的顺式作用元件介导的。利用叶绿体转化技术，将莱茵衣藻野生型petD基因的5'UTR替换为突变版本。含有改变的5'UTR的转化体具有野生型光合表型、渗漏型非光合表型，或者无法进行光合生长。在那些具有野生型表型的转化体中，有些在假定的Shine-Dalgarno序列元件中含有突变。结果表明，362个核苷酸（nt）的5'UTR的两个区域可能作为翻译的正调控元件，一个位于150至200 nt之间，另一个位于起始密码子上游约40 nt处，即320 nt处。在每种翻译受到损害的情况下，petD mRNA的积累水平都低于野生型细胞，不同菌株中的积累水平在15%至60%之间。得出的结论是，petD基因5'UTR的特定区域介导翻译激活，并且mRNA稳定性可能与可翻译性相关。
