Zinc knuckle (ZCCHC) motif-containing proteins are present in unicellular and multicellular eukaryotes, and most ZCCHC proteins with known functions participate in the metabolism of various classes of RNA, such as mRNAs, ribosomal RNAs, and microRNAs. The Arabidopsis (Arabidopsis thaliana) genome encodes 69 ZCCHC-containing proteins; however, the functions of most remain unclear. One of these proteins, CAX-INTERACTING PROTEIN 4 (CXIP4, encoded by AT2G28910), has been classified as a PTHR31437 family member. This family includes human Splicing regulatory glutamine/lysine-rich protein 1 (SREK1)-interacting protein 1 (SREK1IP1), which is thought to function in pre-mRNA splicing and RNA methylation. Metazoan SREK1IP1-like and plant CXIP4-like proteins only share a ZCCHC motif, and their functions remain almost entirely unknown. Here, we studied two loss-of-function alleles of Arabidopsis CXIP4: cxip4-1 is likely null and shows early lethality, and cxip4-2 is hypomorphic and viable, with pleiotropic morphological defects. The cxip4-2 mutant exhibited deregulation of defense genes and upregulation of transcription factor genes, some of which might explain its developmental defects. The cxip4-2 mutant also exhibited increased intron retention events, being more evident in cxip4-1. The specific functions of misspliced genes, such as those involved in “gene silencing by DNA methylation” and “mRNA polyadenylation factor” suggest that CXIP4 has additional functions. In cxip4-2 plants, polyadenylated RNAs accumulate in the nucleus; these could be misspliced mRNAs. The CXIP4 protein localizes to the nucleus in a pattern resembling nuclear speckles rich in splicing factors. Therefore, CXIP4 is required for plant development and survival and mRNA maturation.

中文翻译：

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CAX 相互作用的 PROTEIN4 耗竭导致拟南芥的早期致死和前体 mRNA 错误剪接


含有锌指节 （ZCCHC） 基序的蛋白存在于单细胞和多细胞真核生物中，大多数具有已知功能的 ZCCHC 蛋白参与各种类别 RNA 的代谢，例如 mRNA、核糖体 RNA 和 microRNA。拟南芥 （Arabidopsis thaliana） 基因组编码 69 种含 ZCCHC 的蛋白质;然而，大多数的功能仍不清楚。其中一种蛋白，CAX 相互作用蛋白 4（CXIP4，由 AT2G28910 编码），已被归类为 PTHR31437 家族成员。该家族包括人剪接调节性谷氨酰胺/赖氨酸富集蛋白 1 （SREK1） 相互作用蛋白 1 （SREK1IP1），该蛋白被认为在前体 mRNA 剪接和 RNA 甲基化中发挥作用。后生动物 SREK1IP1 样和植物 CXIP4 样蛋白仅共享一个 ZCCHC 基序，它们的功能几乎完全未知。在这里，我们研究了拟南芥 CXIP4 的两个功能丧失等位基因： cxip4-1 可能是无效的并显示出早期致死性，而 cxip4-2 是亚型且有活力的，具有多效性形态缺陷。cxip4-2 突变体表现出防御基因的失调和转录因子基因的上调，其中一些可能解释了其发育缺陷。cxip4-2 突变体也表现出内含子保留事件增加，在 cxip4-1 中更为明显。错剪接基因的特定功能，例如参与“DNA 甲基化基因沉默”和“mRNA 多聚腺苷酸化因子”的基因，表明 CXIP4 具有额外的功能。在 cxip4-2 植物中，多聚腺苷酸化 RNA 在细胞核中积累;这些可能是错误剪接的 mRNA。CXIP4 蛋白以类似于富含剪接因子的核斑点的模式定位于细胞核。因此，CXIP4 是植物发育和存活以及 mRNA 成熟所必需的。