Nielsen Henrik, Wernersson Rasmus
Center for Biological Sequence Analysis, Technical University of Denmark, Building 208, 2800 Lyngby, Denmark.
BMC Genomics. 2006 Oct 11;7:256. doi: 10.1186/1471-2164-7-256.
A knowledge of the positions of introns in eukaryotic genes is important for understanding the evolution of introns. Despite this, there has been relatively little focus on the distribution of intron positions in genes.
In proteins with signal peptides, there is an overabundance of phase 1 introns around the region of the signal peptide cleavage site. This has been described before. But in proteins without signal peptides, a novel phenomenon is observed: There is a sharp peak of phase 0 intron positions immediately following the start codon, i.e. between codons 1 and 2. This effect is seen in a wide range of eukaryotes: Vertebrates, arthropods, fungi, and flowering plants. Proteins carrying this start codon intron are found to comprise a special class of relatively short, lysine-rich and conserved proteins with an overrepresentation of ribosomal proteins. In addition, there is a peak of phase 0 introns at position 5 in Drosophila genes with signal peptides, predominantly representing cuticle proteins.
There is an overabundance of phase 0 introns immediately after the start codon in eukaryotic genes, which has been described before only for human ribosomal proteins. We give a detailed description of these start codon introns and the proteins that contain them.
了解内含子在真核基因中的位置对于理解内含子的进化很重要。尽管如此，人们对基因中内含子位置的分布关注相对较少。
在具有信号肽的蛋白质中，信号肽切割位点区域周围存在过多的1相内含子。这一点之前已有描述。但在没有信号肽的蛋白质中，观察到一种新现象：起始密码子之后紧接着存在0相内含子位置的一个尖峰，即位于密码子1和2之间。这种效应在广泛的真核生物中都可见：脊椎动物、节肢动物、真菌和开花植物。发现携带这种起始密码子内含子的蛋白质构成一类特殊的相对较短、富含赖氨酸且保守的蛋白质，其中核糖体蛋白占比过高。此外，在具有信号肽的果蝇基因中，0相内含子在第5位存在一个尖峰，主要代表表皮蛋白。
真核基因中起始密码子之后紧接着存在过多的0相内含子，此前仅在人类核糖体蛋白中有所描述。我们对这些起始密码子内含子以及包含它们的蛋白质进行了详细描述。
