Vaidyanathan Pavanapuresan P, Deutscher Murray P, Malhotra Arun
Department of Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL 33101-6129, USA.
RNA. 2007 Nov;13(11):1868-76. doi: 10.1261/rna.711207. Epub 2007 Sep 13.
Pseudouridine modifications in helix 69 (H69) of 23S ribosomal RNA are highly conserved among all organisms. H69 associates with helix 44 of 16S rRNA to form bridge B2a, which plays a vital role in bridging the two ribosomal subunits and stabilizing the ribosome. The three pseudouridines in H69 were shown earlier to play an important role in 50S subunit assembly and in its association with the 30S subunit. In Escherichia coli, these three modifications are made by the pseudouridine synthase, RluD. Previous work showed that RluD is required for normal ribosomal assembly and function, and that it is the only pseudouridine synthase required for normal growth in E. coli. Here, we show that RluD is far more efficient in modifying H69 in structured 50S subunits, compared to free or synthetic 23S rRNA. Based on this observation, we suggest that pseudouridine modifications in H69 are made late in the assembly of 23S rRNA into mature 50S subunits. This is the first reported observation of a pseudouridine synthase being able to modify a highly structured ribonucleoprotein particle, and it may be an important late step in the maturation of 50S ribosomal subunits.
23S核糖体RNA螺旋69（H69）中的假尿苷修饰在所有生物中高度保守。H69与16S rRNA的螺旋44结合形成桥B2a，这在连接两个核糖体亚基和稳定核糖体方面起着至关重要的作用。先前研究表明，H69中的三个假尿苷在50S亚基组装及其与30S亚基的结合中发挥重要作用。在大肠杆菌中，这三种修饰由假尿苷合酶RluD完成。先前的工作表明，RluD是正常核糖体组装和功能所必需的，并且它是大肠杆菌正常生长所需的唯一假尿苷合酶。在此，我们表明，与游离或合成的23S rRNA相比，RluD在修饰结构化50S亚基中的H69方面效率要高得多。基于这一观察结果，我们认为H69中的假尿苷修饰是在23S rRNA组装成成熟50S亚基的后期进行的。这是首次报道假尿苷合酶能够修饰高度结构化的核糖核蛋白颗粒，并且这可能是50S核糖体亚基成熟过程中的一个重要后期步骤。
