Choi SeokGyeong, Ha Sojung, Wolfgeher Donald J, Kim Jee Won, Go Young-Hyun, Cha Hyuk-Jin, Bae Gyu-Un, Kron Stephen J, Kim Woo-Young
Muscle Physiome Research Center, Sookmyung Women's University, Seoul 04310, Republic of Korea; College of Pharmacy, Sookmyung Women's University, Seoul 04310, Republic of Korea.
Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL, USA.
Mol Cells. 2025 Jul 1;48(9):100250. doi: 10.1016/j.mocell.2025.100250.
Four isoform peptides of the novel E3 ligase ring finger protein 220 (RNF220) have been identified in humans. However, all of the previous studies have predominantly focused on isoform 1 (the full-length form), which consists of 566 amino acids. Here, we show that a shorter isoform, which is 308 amino acids lacking most of the N-terminus (human isoform 4; mouse isoform 3; ΔN-RNF220), is the predominant and ubiquitously expressed variant that warrants functional investigation. Both isoform 1 and ΔN-RNF220 are expressed in the brain; however, ΔN-RNF220 is the major isoform expressed in all other tissues in mice. Consistently, H3K4me3 ChIP-seq data from ENCODE reveal that the transcription start site for ΔN-RNF220 demonstrates broader and stronger activity across human tissues than that of isoform 1. ΔN-RNF220 produces 2 peptides (4a and 4b) through alternative translation initiation, with isoform 4b displaying distinct subcellular localization, subnuclear structures and interaction with a nuclear protein WDR5. Notably, during embryonic stem cell differentiation into neural stem cells, isoform 1 expression increases, whereas ΔN-RNF220 expression decreases. In murine myoblasts, ΔN-RNF220 is the sole expressed isoform and is required for MyoD and myogenin expression, as well as for muscle differentiation. Our findings highlight ΔN-RNF220 as the ubiquitously and highly expressed variant, likely playing a fundamental role across tissues while exhibiting functional differences from isoform 1. These results emphasize the critical importance of ΔN-RNF220 in future studies investigating the biological functions of RNF220.
在人类中已鉴定出新型E3连接酶环指蛋白220（RNF220）的四种同工型肽。然而，之前所有的研究主要集中在由566个氨基酸组成的同工型1（全长形式）上。在此，我们表明一种较短的同工型，即缺少大部分N端的308个氨基酸（人类同工型4；小鼠同工型3；ΔN-RNF220），是主要且普遍表达的变体，值得进行功能研究。同工型1和ΔN-RNF220均在大脑中表达；然而，ΔN-RNF220是小鼠所有其他组织中表达的主要同工型。一致地，来自ENCODE的H3K4me3 ChIP-seq数据显示，与同工型1相比，ΔN-RNF220的转录起始位点在人类组织中表现出更广泛、更强的活性。ΔN-RNF220通过可变翻译起始产生2种肽（4a和4b），同工型4b表现出不同的亚细胞定位、亚核结构以及与核蛋白WDR5的相互作用。值得注意的是，在胚胎干细胞分化为神经干细胞的过程中，同工型1的表达增加，而ΔN-RNF220的表达减少。在小鼠成肌细胞中 , ΔN-RNF220是唯一表达的同工型，是MyoD和肌细胞生成素表达以及肌肉分化所必需的。我们的研究结果突出了ΔN-RNF220作为普遍且高表达的变体，可能在各个组织中发挥重要作用，同时表现出与同工型1的功能差异。这些结果强调了ΔN-RNF220在未来研究RNF220生物学功能中的至关重要性。
