Moreno-Rodríguez Antonio, Pérez-Pulido Antonio J, Mier Pablo
Andalusian Centre for Developmental Biology (CABD, UPO-CSIC-JA), Faculty of Experimental Sciences (Genetics Area), Universidad Pablo de Olavide, 41013 Seville, Spain.
NAR Genom Bioinform. 2025 Jun 9;7(2):lqaf075. doi: 10.1093/nargab/lqaf075. eCollection 2025 Jun.
Polyglutamine regions appear in many eukaryotic proteins. Most research on these stretches has focused on humans and primates. We wanted to check whether patterns in their codon usage are shared across a wide taxonomic range. Protein-coding transcripts from 30 eukaryotic model species were searched for stretches of consecutive glutamine codons (CAA/CAG). Most species have higher CAG proportion in longer stretches, except fishes, which either reduced or kept a stable CAG use. CAA codons are located closer to the C-terminal side of the stretches in plants, invertebrates, and tetrapods; fungi showed no bias and fishes showed the opposite. Many tetrapods have codons flanking pure CAG stretches that hint at a mutational control of repeat growth. However, the maximum number of consecutive identical codons within the polyglutamine stretches in most species followed random expectations, with fishes as a main exception. We detected shared patterns in codon usage and position across taxonomically distant species, yet each group retained unique traits. Internal CAA position and external flanking codons both seemed to slow pure CAG expansion. Overall, a mix of random processes and species-specific factors drives how glutamine repeats are shaped and maintained in evolution.
多聚谷氨酰胺区域出现在许多真核生物蛋白质中。对这些片段的大多数研究都集中在人类和灵长类动物上。我们想检查它们的密码子使用模式是否在广泛的分类范围内共享。在30种真核模式生物的蛋白质编码转录本中搜索连续的谷氨酰胺密码子（CAA/CAG）片段。除鱼类外，大多数物种在较长片段中CAG比例更高，鱼类要么CAG使用减少，要么保持稳定。在植物、无脊椎动物和四足动物中，CAA密码子位于片段的更靠近C末端一侧；真菌没有偏向性，而鱼类则相反。许多四足动物在纯CAG片段两侧有密码子，这暗示了对重复序列增长的突变控制。然而，大多数物种的多聚谷氨酰胺片段内连续相同密码子的最大数量符合随机预期，鱼类是主要例外。我们在分类学上相距甚远的物种中检测到了密码子使用和位置的共享模式，但每个类群都保留了独特的特征。内部CAA位置和外部侧翼密码子似乎都减缓了纯CAG的扩展。总体而言，随机过程和物种特异性因素的混合驱动了谷氨酰胺重复序列在进化中如何形成和维持。
