Biotechnology Centre of Oslo, University of Oslo, Norway.
J Biol Chem. 2009 Dec 11;284(50):35154-64. doi: 10.1074/jbc.M109.056465. Epub 2009 Oct 19.
Protein kinase A (PKA) is targeted to distinct subcellular localizations by specific protein kinase A anchoring proteins (AKAPs). AKAPs are divided into subclasses based on their ability to bind type I or type II PKA or both. Dual-specificity AKAPs were recently reported to have an additional PKA binding determinant called the RI specifier region. A bioinformatic search with the consensus RI specifier region identified a novel AKAP, the splicing factor arginine/serine-rich 17A (SFRS17A). Here, we show by a variety of protein interaction assays that SFRS17A binds both type I and type II PKA in vitro and inside cells, demonstrating that SFRS17A is a dual-specific AKAP. Moreover, immunofluorescence experiments show that SFRS17A colocalizes with the catalytic subunit of PKA as well as the splicing factor SC35 in splicing factor compartments. Using the E1A minigene splicing assay, we found that expression of wild type SFRS17A conferred regulation of E1A alternative splicing, whereas the mutant SFRS17A, which is unable to bind PKA, did not. Our data suggest that SFRS17A is an AKAP involved in regulation of pre-mRNA splicing possibly by docking a pool of PKA in splicing factor compartments.
蛋白激酶 A(PKA)通过特定的蛋白激酶 A 锚定蛋白(AKAP)靶向到不同的亚细胞定位。AKAP 根据其结合 I 型或 II 型 PKA 或两者的能力分为不同的亚类。最近有报道称,双特异性 AKAP 具有一个额外的 PKA 结合决定簇,称为 RI 特异性区域。使用共识 RI 特异性区域的生物信息学搜索确定了一种新的 AKAP,即剪接因子精氨酸/丝氨酸富含 17A(SFRS17A)。在这里,我们通过各种蛋白质相互作用实验表明,SFRS17A 在体外和细胞内均结合 I 型和 II 型 PKA,证明 SFRS17A 是一种双特异性 AKAP。此外,免疫荧光实验表明,SFRS17A 与 PKA 的催化亚基以及剪接因子 SC35 在剪接因子隔室中共定位。使用 E1A 小基因剪接测定,我们发现野生型 SFRS17A 的表达赋予了 E1A 可变剪接的调节,而不能结合 PKA 的突变型 SFRS17A 则没有。我们的数据表明,SFRS17A 是一种 AKAP,可能通过将 PKA 池停靠在剪接因子隔室中来参与调节前体 mRNA 的剪接。