背景:端粒由染色体末端的重复DNA序列组成,以保护染色体稳定性,并且主要通过端粒酶或偶尔通过基于重组的机制通过端粒的替代端粒延长(ALT)来维持。可能调节端粒维持的其他机制仍有待探索。同时测量同一人胚胎干细胞(hESC)中的端粒长度和转录组,表明UBQLN1的mRNA表达水平与端粒长度呈线性关系。
方法:在本研究中,我们首先产生了UBQLN1缺陷型hESCs,并通过RNA-seq和蛋白质组学与野生型(WT)hESCs比较了端粒长度和RNA和蛋白质水平的分子变化.然后,我们使用免疫沉淀-质谱(IP-MS)鉴定了与UBQLN1的潜在相互作用蛋白。此外,分析了UBQLN1缺陷型hESCs端粒缩短的潜在机制.
结果:我们表明Ubiquilin1(UBQLN1)通过促进线粒体功能对人胚胎干细胞(hESCs)的端粒维持至关重要。UBQLN1缺乏导致氧化应激,失去了蛋白质,线粒体功能障碍,DNA损伤,和端粒磨耗。通过在低氧条件下培养或补充N-乙酰半胱氨酸来减少氧化损伤并促进线粒体功能,部分减轻了UBQLN1缺乏症诱导的端粒磨耗。此外,UBQLN1缺乏/端粒缩短下调神经外胚层谱系分化的基因。
结论:总而言之,UBQLN1功能清除泛素化蛋白,防止线粒体过载和线粒体自噬升高。UBQLN1通过调节蛋白抑制维持线粒体和端粒,并在神经外胚层分化中起关键作用。
BACKGROUND: Telomeres consist of repetitive DNA sequences at the chromosome ends to protect chromosomal stability, and primarily maintained by telomerase or occasionally by alternative telomere lengthening of telomeres (ALT) through recombination-based mechanisms. Additional mechanisms that may regulate telomere maintenance remain to be explored. Simultaneous measurement of telomere length and transcriptome in the same human embryonic stem cell (hESC) revealed that mRNA expression levels of UBQLN1 exhibit linear relationship with telomere length.
METHODS: In this study, we first generated UBQLN1-deficient hESCs and compared with the wild-type (WT) hESCs the telomere length and molecular change at RNA and protein level by RNA-seq and proteomics. Then we identified the potential interacting proteins with UBQLN1 using immunoprecipitation-mass spectrometry (IP-MS). Furthermore, the potential mechanisms underlying the shortened telomeres in UBQLN1-deficient hESCs were analyzed.
RESULTS: We show that Ubiquilin1 (UBQLN1) is critical for telomere maintenance in human embryonic stem cells (hESCs) via promoting mitochondrial function. UBQLN1 deficiency leads to oxidative stress, loss of proteostasis, mitochondria dysfunction, DNA damage, and telomere attrition. Reducing oxidative damage and promoting mitochondria function by culture under hypoxia condition or supplementation with N-acetylcysteine partly attenuate the telomere attrition induced by UBQLN1 deficiency. Moreover, UBQLN1 deficiency/telomere shortening downregulates genes for neuro-ectoderm lineage differentiation.
CONCLUSIONS: Altogether, UBQLN1 functions to scavenge ubiquitinated proteins, preventing their overloading mitochondria and elevated mitophagy. UBQLN1 maintains mitochondria and telomeres by regulating proteostasis and plays critical role in neuro-ectoderm differentiation.