Howell Viive M, Jones Julie M, Bergren Sarah K, Li Li, Billi Allison C, Avenarius Matthew R, Meisler Miriam H
Department of Human Genetics, University of Michigan School of Medicine, Ann Arbor, MI 48109-0618, USA.
Hum Mol Genet. 2007 Oct 15;16(20):2506-16. doi: 10.1093/hmg/ddm206. Epub 2007 Jul 26.
We originally isolated Scnm1 as a disease modifier gene that is required for efficient in vivo splicing of a mutant splice donor site in the sodium channel Scn8a. It was previously unclear whether the modifier effect on splicing was direct or indirect. We now report evidence that sodium channel modifier 1 (SCNM1) has a direct role in splicing. SCNM1 protein interacts with the spliceosome protein U1-70K in the yeast two-hybrid system, and is co-localized with U1-70K in nuclear speckles in mammalian cells. SCNM1 is also co-immunoprecipitated with the spliceosomal core Smith (Sm) proteins and demonstrates functional activity in a minigene splicing assay. In a yeast two-hybrid screen, SCNM1 interacted with LUC7L2, a mammalian homolog of a yeast protein involved in recognition of non-consensus splice donor sites. This interaction requires the acidic C-terminal domain of SCNM1 which is truncated by the disease susceptibility variant Scnm1(R187X) in mouse strain C57BL/6J. Luc7L2 transcripts are widely distributed in mammalian tissues, and undergo alternative splicing and polyadenylation. LUC7L2 is also co-localized with U1-70K and may function with SCNM1 in recognition of weak splice donor sites. In summary, Scnm1 is the first example of a modifier gene which influences disease severity through a trans-effect on splicing of the disease gene transcript.
我们最初将Scnm1分离为一种疾病修饰基因，它是钠通道Scn8a中突变剪接供体位点在体内高效剪接所必需的。此前尚不清楚其对剪接的修饰作用是直接的还是间接的。我们现在报告证据表明，钠通道修饰因子1（SCNM1）在剪接中具有直接作用。在酵母双杂交系统中，SCNM1蛋白与剪接体蛋白U1 - 70K相互作用，并且在哺乳动物细胞的核斑点中与U1 - 70K共定位。SCNM1还与剪接体核心史密斯（Sm）蛋白进行共免疫沉淀，并在小基因剪接试验中显示出功能活性。在酵母双杂交筛选中，SCNM1与LUC7L2相互作用，LUC7L2是一种酵母蛋白的哺乳动物同源物，参与非共识剪接供体位点的识别。这种相互作用需要SCNM1的酸性C末端结构域，而在小鼠品系C57BL / 6J中，该结构域被疾病易感性变体Scnm1(R187X)截断。Luc7L2转录本广泛分布于哺乳动物组织中，并经历可变剪接和多聚腺苷酸化。LUC7L2也与U1 - 70K共定位，并且可能与SCNM1一起在识别弱剪接供体位点中发挥作用。总之，Scnm1是修饰基因的第一个例子，它通过对疾病基因转录本剪接的反式作用影响疾病严重程度。
