PCBP1 and PCBP2 both bind heavily oxidized RNA but cause opposing outcomes, suppressing or increasing apoptosis under oxidative conditions
PCBP1 and PCBP2 both bind heavily oxidized RNA but cause opposing outcomes, suppressing or increasing apoptosis under oxidative conditions
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DOI：
10.1074/jbc.ra119.011870
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发表时间：
2020-08-21
影响因子：
4.8
通讯作者：
Nakabeppu, Yusaku
中科院分区：
文献类型：
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作者：
Ishii, Takashi;Igawa, Tatsuhiro;Nakabeppu, Yusaku
PCBP1 是聚 (C) 结合蛋白 (PCBP) 家族的成员，具有结合严重氧化的 RNA 的能力，因此参与细胞对氧化条件的反应，有助于诱导细胞凋亡。该家族还有其他四个成员，PCBP2、PCBP3、PCBP4和hnRNPK，但尚不清楚它们是否发挥相似的作用。为了了解更多信息，我们首先测试了它们对在彼此靠近的位点上携带两个 8-氧鸟嘌呤 (8-oxoG) 残基的 RNA 链的亲和力，代表重度氧化的链或具有一个 8-oxoG 或没有 8-oxoG 的 RNA。其中，只有 PCBP2 表现出与携带两个 8-oxoG 残基的 RNA 的高度选择性结合，类似于 PCBP1 观察到的情况。相比之下，PCBP3、PCBP4和hnRNPK结合有或没有8-oxoG修饰的RNA，并且与前者的结合略有增加。 PCBP2 保守的 RNA 结合域的突变破坏了与严重氧化的 RNA 的特异性相互作用。接下来我们测试了细胞中的 PCBP2 活性。与WT HeLa S3细胞相比，通过基因编辑建立的PCBP2-KO细胞表现出细胞凋亡增加，氧化条件下caspase-3活性增加，PARP1裂解增加，这种情况被WT PCBP2的表达抑制，但没有一种缺乏结合活性的突变体。相反，PCBP1-KO 细胞表现出细胞凋亡减少，caspase-3 活性和 PARP 裂解比 WT 细胞少得多。我们的结果表明 PCBP2 和 PCBP1 结合重度氧化的 RNA；然而，前者可能会抵消 PCBP1 以抑制氧化条件下的细胞凋亡。
PCBP1, a member of the poly(C)-binding protein (PCBP) family, has the capability of binding heavily oxidized RNA and therefore participates in the cellular response to oxidative conditions, helping to induce apoptosis. There are four other members of this family, PCBP2, PCBP3, PCBP4, and hnRNPK, but it is not known whether they play similar roles. To learn more, we first tested their affinity for an RNA strand carrying two 8-oxoguanine (8-oxoG) residues at sites located in close proximity to each other, representative of a heavily oxidized strand or RNA with one 8-oxoG or none. Among them, only PCBP2 exhibited highly selective binding to RNA carrying two 8-oxoG residues similar to that observed with PCBP1. In contrast, PCBP3, PCBP4, and hnRNPK bound RNA with or without 8-oxoG modifications and exhibited slightly increased binding to the former. Mutations in conserved RNA-binding domains of PCBP2 disrupted the specific interaction with heavily oxidized RNA. We next tested PCBP2 activity in cells. Compared with WT HeLa S3 cells, PCBP2-KO cells established by gene editing exhibited increased apoptosis with increased caspase-3 activity and PARP1 cleavage under oxidative conditions, which were suppressed by the expression of WT PCBP2 but not one of the mutants lacking binding activity. In contrast, PCBP1-KO cells exhibited reduced apoptosis with much less caspase-3 activity and PARP cleavage than WT cells. Our results indicate that PCBP2 as well as PCBP1 bind heavily oxidized RNA; however, the former may counteract PCBP1 to suppress apoptosis under oxidative conditions.