Department of Basic Medical Sciences, College of Medicine-Phoenix, University of Arizona, Phoenix, Arizona 85004, USA.
Department of Basic Medical Sciences, College of Medicine-Phoenix, University of Arizona, Phoenix, Arizona 85004, USA
RNA. 2024 Feb 16;30(3):271-280. doi: 10.1261/rna.079892.123.
The human U1 snRNA is encoded by a multigene family consisting of transcribed variants and defective pseudogenes. Many variant U1 (vU1) snRNAs have been demonstrated to not only be transcribed but also processed by the addition of a trimethylated guanosine cap, packaged into snRNPs, and assembled into spliceosomes; however, their capacity to facilitate pre-mRNA splicing has, so far, not been tested. A recent systematic analysis of the human snRNA genes identified 178 U1 snRNA genes that are present in the genome as either tandem arrays or single genes on multiple chromosomes. Of these, 15 were found to be expressed in human tissues and cell lines, although at significantly low levels from their endogenous loci, <0.001% of the canonical U1 snRNA. In this study, we found that placing the variants in the context of the regulatory elements of the gene improves the expression of many variants to levels comparable to the canonical U1 snRNA. Application of a previously established HeLa cell-based minigene reporter assay to examine the capacity of the vU1 snRNAs to support pre-mRNA splicing revealed that even though the exogenously expressed variant snRNAs were enriched in the nucleus, only a few had a measurable effect on splicing.
人类 U1 snRNA 由一个多基因家族编码，该家族由转录变体和缺陷假基因组成。许多变体 U1（vU1）snRNA 不仅被转录，而且通过添加三甲基鸟苷帽进行加工，包装成 snRNPs，并组装到剪接体中；然而，它们促进前体 mRNA 剪接的能力尚未得到测试。最近对人类 snRNA 基因的系统分析确定了 178 个 U1 snRNA 基因，这些基因存在于基因组中，要么是串联排列，要么是多个染色体上的单个基因。其中，有 15 个在人类组织和细胞系中表达，尽管其在自身基因座上的表达水平非常低，<0.001%的是典型的 U1 snRNA。在这项研究中，我们发现将变体置于基因的调节元件的背景下可以提高许多变体的表达水平，使其与典型的 U1 snRNA 相当。应用先前建立的基于 HeLa 细胞的小基因报告基因检测，检查 vU1 snRNA 支持前体 mRNA 剪接的能力，结果表明，尽管外源性表达的变体 snRNA 在核内富集，但只有少数变体对剪接有可测量的影响。
