背景:异质核核糖核蛋白K(HNRNPK)调节前mRNA加工和长非编码RNA在细胞核中的定位。先前显示HNRNPK穿梭到细胞质促进细胞增殖和癌症转移。然而,HNRNPK细胞质定位的机制,它的细胞质RNA配体,对转录后基因调控的影响仍未表征。
结果:在这里,我们表明中间丝蛋白角蛋白19(K19)直接与HNRNPK相互作用,并将其隔离在细胞质中。相应地,在K19基因敲除的乳腺癌细胞中,HNRNPK不定位在细胞质中,导致细胞增殖减少。我们在mRNAs上全面定位了HNRNPK结合位点,在细胞质中,K19介导的HNRNPK保留增加了与预期的富含胞苷(富含C)序列元件处的3'非翻译区(3'UTR)结合的靶mRNA的丰度。此外,这些在细胞质中被HNRNPK保护的mRNA通常与癌症进展有关,并且包括在HNRNPK敲低(HNRNPKKD)或K19敲除(KRT19KO)时失调的p53信号通路.
结论:本研究确定了细胞骨架蛋白如何通过控制RNA结合蛋白的亚细胞定位来直接调节基因表达,以支持参与癌症进展的途径。
BACKGROUND: Heterogeneous nuclear ribonucleoprotein K (HNRNPK) regulates pre-mRNA processing and long non-coding RNA localization in the nucleus. It was previously shown that shuttling of HNRNPK to the cytoplasm promotes cell proliferation and cancer metastasis. However, the mechanism of HNRNPK cytoplasmic localization, its cytoplasmic RNA ligands, and impact on post-transcriptional gene regulation remain uncharacterized.
RESULTS: Here we show that the intermediate filament protein Keratin 19 (K19) directly interacts with HNRNPK and sequesters it in the cytoplasm. Correspondingly, in K19 knockout breast cancer cells, HNRNPK does not localize in the cytoplasm, resulting in reduced cell proliferation. We comprehensively mapped HNRNPK binding sites on mRNAs and showed that, in the cytoplasm, K19-mediated HNRNPK-retention increases the abundance of target mRNAs bound to the 3\' untranslated region (3\'UTR) at the expected cytidine-rich (C-rich) sequence elements. Furthermore, these mRNAs protected by HNRNPK in the cytoplasm are typically involved in cancer progression and include the p53 signaling pathway that is dysregulated upon HNRNPK knockdown (HNRNPK KD) or K19 knockout (KRT19 KO).
CONCLUSIONS: This study identifies how a cytoskeletal protein can directly regulate gene expression by controlling the subcellular localization of RNA-binding proteins to support pathways involved in cancer progression.