LIN28 protein and let-7 family micro RNAs (miRNAs) that are an evolutionarily conserved from nematodes to humans are the important regulators of developmental timing by dynamically interacting with each other. However, regulators of LIN28 remain largely elusive. Here, we show the evidences that Sjögren Syndrome antigen B (SSB) protein associates and cooperates with LIN28A and LIN28B, mammalian orthologues of Caenorhabditis elegans lin-28, proteins in the nucleus. Knockdown of SSB in HEK293 cell line resulted in the decrease of the amount of LIN28B mRNAs and proteins, and the increase of the level of mature let-7 miRNAs. Furthermore, RNA interference of ssb-1 gene, a worm SSB orthologue, was sufficient to cause a heterochronic defect in seam cells of C. elegans, recapitulating the phenotype of lin-28 downregulation. Collectively, we suggest that SSB is an important regulator for the LIN28-let-7 axis.

从线虫到人类进化保守的LIN28蛋白和let-7家族微RNA（miRNA）是彼此动态相互作用的重要发育调控因子。但是，LIN28的调节器仍然难以捉摸。在这里，我们显示Sjögren综合征抗原B（SSB）蛋白与LIN28A和LIN28B，秀丽隐杆线虫lin-28哺乳动物直系同源物，在细胞核中相关联并协同作用的证据。敲除HEK293细胞系中的SSB导致LIN28B mRNA和蛋白的量减少，而成熟let-7 miRNA的水平增加。此外，ssb-1的RNA干扰蠕虫SSB直系同源基因，足以在秀丽隐杆线虫的接缝细胞中引起异时性缺陷，概括了lin-28下调的表型。总之，我们建议SSB是LIN28 -let-7轴的重要调节器。