Panaro Maria A, Cianciulli Antonia, Calvello Rosa, Saccia Matteo, Sisto Margherita, Acquafredda Angela, Mitolo Vincenzo
Department of Human Anatomy and Histology, University of Bari, Italy.
Immunopharmacol Immunotoxicol. 2009;31(1):88-93. doi: 10.1080/08923970802372863.
In this article we analyze some of the structural characteristics of the coding section and the intron of the human chemokine CXC receptor 4 (a 7-transmembrane receptor) pre-mRNA. In the coding sequence the frequencies of the individual nucleotides do not depart significantly from 0.25, while in the intron the frequencies of the As and Gs are significantly lower and higher, respectively, than expected from a random distribution. Analysis of the pattern of association of nucleotides into triplets or couples shows that some triplets or couples occur with frequencies significantly higher or lower than expected when assuming a random association of nucleotides. In particular, in the intron combinations of the same nucleotide are over-represented. 7-or-more nucleotide repeats occur in both the coding section and the intron with frequencies which exceed the confidence limits for a random distribution. For the coding sequence this is possibly explained by the alternans of relatively similar hydrophobic-coding sections and relatively similar intervening intracellular and extracellular hydrophilic-coding sections. 7-or-more nucleotide repeats in reverse order and in reverse/complemented order occur in the intron, but not in the coding section, with frequencies which significantly exceed a random distribution. The numerous intronic repeats in reverse/complemented order may be of relevance for the secondary structure of the intron and might be one important element of the integrated splicing code.
在本文中，我们分析了人类趋化因子CXC受体4（一种7跨膜受体）前体mRNA编码区和内含子的一些结构特征。在编码序列中，单个核苷酸的频率与0.25相比没有显著差异，而在内含子中，A和G的频率分别显著低于和高于随机分布的预期值。对核苷酸三联体或二联体的关联模式分析表明，当假设核苷酸随机关联时，一些三联体或二联体出现的频率显著高于或低于预期。特别是，相同核苷酸在内含子中的组合出现频率过高。7个或更多核苷酸的重复序列在编码区和内含子中均有出现，其频率超过了随机分布的置信限。对于编码序列，这可能是由相对相似的疏水编码区以及相对相似的细胞内和细胞外亲水编码区的交替所解释的。7个或更多核苷酸的反向重复序列以及反向/互补重复序列在内含子中出现，但在编码区中不出现，其频率显著超过随机分布。大量的反向/互补内含子重复序列可能与内含子的二级结构有关，并且可能是综合剪接密码的一个重要元素。
