摘要
在SL反式剪接过程中,生物利用SL RNA分子上的SD位点和pre-mRNA分子上的SA位点,在剪接体的作用下,将SL作为小型外显子加到pre-mRNA上形成成熟的mRNA。SL反式剪接这一古老的生物学过程在那些进化缓慢的分子中被完整地保留了下来。不同生物间的SL在大小和组成上有时差别很大;个别生物中还存在着组成完全不同的两种SL,它们在pre-mRNA的加工过程中有着不同的作用。几乎所有的SL RNA在结构上有着惊人的相似之处,包括5’末端的TMG帽子结构、保守的SD位点、Sm位点、SL RNA二级结构等。由于pre-mRNA在转录过程中丢失了SA位点或获得了SD位点,大多数脊椎动物在进化过程中丢失了SL反式剪接方式,而这种丢失可能是导致脊椎动物C值增高的原因之一。
In the process of SL （ spliced leader） trans-splicing,with the help of spliceosome, SL as a mini-exon is added to the 5 ＇ -end of pre-mRNA to mature mRNA through the sites SD in SL RNA and SA in pre-mRNA. This modification pattern of pre-mRNA is completely retained in evolutionarily conservative molecules. Sometimes, the size of SL from different organisms is greatly different, and, in some creature, there are two different SLs that play different roles in the process of pre-mRNA. Although the nucleotide constituent of different SL RNAs varies significantly, their structures show high similarity, such as a TMG cap at the 5 ＇ -terminal, conservative sites SD and Sm, the secondary structure of SL RNA. The phenomenon of SL trans-splicing has crucially evolutionary significance. Because of the loss of SA site or the gain of SD site in the transcriptional process of pre-mRNA, the SL trans-splicing way is discarded in evolution in most vertebrates. The lack may be one of the reasons that give rise to the increase of C value.
出处
《实验室研究与探索》
CAS
2008年第1期17-21,98,共6页
Research and Exploration In Laboratory
基金
国家重大基础研究发展规划"973"项目(G1999011906)
