The mouse 3110001I22Rik gene located in the first intron of Bfar is considered as a Bfar variant coding for the BFARv3 protein. However, it differs from other BFAR isoforms and resembles periphilin 1 (PPHLN1) due to its two (Lge1 and serine-rich) conserved domains. We identified the BFARv3/EGFP-interacting proteins by co-immunoprecipitation coupled to mass spectrometry, which revealed 40S ribosomal proteins (RPS3, RPS14, RPS19, RPS25, RPS27), histones (H1.2, H1.4, H3.3C), proteins involved in RNA processing and splicing (SFPQ, SNRPA1, HNRNPA3, NONO, KHDRBS3), calcium signaling (HPCAL1, PTK2B), as well as HSD17B4, GRB14, POSTN, and MYO10. Co-immunoprecipitation revealed that both Lge1 and Ser-rich domains of BFARv3 were necessary for binding to RNA-interacting factors NONO and SFPQ, known to be components of paraspeckles. Reciprocal co-immunoprecipitation and the proximity ligation assay confirmed that both BFARv3 and PPHLN1 could interact with NONO and SFPQ, suggesting a new function for PPHLN1 as well. BFARv3 and its Lge1 or Ser-rich-deficient mutants preferentially localize in the nucleus. We found an accumulation of BFARv3/EGFP (but not its mutated forms) in the nuclear granules, which was enhanced in response to arsenite treatment and ionizing radiation. Although Bfar v3 is expressed ubiquitously in mouse tissues, its expression is the highest in metaphase II oocytes. The BFARv3 interactome suggests its role in RNA metabolism, which is critical for the transcriptionally silent MII oocyte. Mouse BFARv3 has no ortholog in the human genome, thus it may contribute to the differences between these two species observed in oocyte maturation and early embryonic development.

鼠标3110001I22Rik位于第一内含子基因BFAR被认为是一个BFARBFARv3 蛋白的变异编码。然而，它与其他 BFAR 亚型不同，并且由于其两个（Lge1 和富含丝氨酸的）保守结构域而类似于 periphilin 1 (PPHLN1)。我们通过与质谱联用的共免疫沉淀法鉴定了 BFARv3/EGFP 相互作用蛋白，这揭示了 40S 核糖体蛋白（RPS3、RPS14、RPS19、RPS25、RPS27）、组蛋白（H1.2、H1.4、H3.3C）、参与 RNA 加工和剪接的蛋白质（SFPQ、SNRPA1、HNRNPA3、NONO、KHDRBS3）、钙信号（HPCAL1、PTK2B）以及 HSD17B4、GRB14、POSTN 和 MYO10。免疫共沉淀表明，BFARv3 的 Lge1 和 Ser-rich 结构域对于与 RNA 相互作用因子 NONO 和 SFPQ（已知是副斑点的组成部分）结合是必需的。相互免疫共沉淀和邻近连接试验证实 BFARv3 和 PPHLN1 都可以与 NONO 和 SFPQ 相互作用，这也表明 PPHLN1 具有新功能。BFARv3 及其 Lge1 或富含 Ser 的缺陷突变体优先定位于细胞核中。我们发现 BFARv3/EGFP（但不是其突变形式）在核颗粒中的积累，其在亚砷酸盐处理和电离辐射的反应中得到增强。虽然Bfar v3在小鼠组织中普遍表达，在中期II期卵母细胞中表达最高。BFARv3 相互作用组表明其在 RNA 代谢中的作用，这对转录沉默的 MII 卵母细胞至关重要。小鼠 BFARv3 在人类基因组中没有直系同源物，因此它可能有助于在卵母细胞成熟和早期胚胎发育中观察到的这两个物种之间的差异。