Summary
Nε -lysine acetylation represents a highly dynamic and reversibly regulated post-translational modification widespread in almost all organisms, and plays important roles for regulation of protein function in diverse metabolic pathways. However, little is known about the role of lysine acetylation in photosynthetic eukaryotic microalgae. We integrated proteomic approaches to comprehensively characterize the lysine acetylome in the model diatom Phaeodactylum tricornutum. In total, 2324 acetylation sites from 1220 acetylated proteins were identified, representing the largest dataset of the lysine acetylome in plants to date. Almost all enzymes involved in fatty acid synthesis were found to be lysine acetylated. Six putative lysine acetylation sites were identified in a plastid-localized long-chain acyl-CoA synthetase. Site-directed mutagenesis and site-specific incorporation of N-acetyllysine in acyl-CoA synthetase show that acetylation at K407 and K425 increases its enzyme activity. Moreover, the nonenzymatically catalyzed overall hyperacetylation of acyl-CoA synthetase by acetyl-phosphate can be effectively deacetylated and reversed by a sirtuin-type NAD + -dependent deacetylase with subcellular localization of both the plastid and nucleus in Phaeodactylum. This work indicates the regulation of acyl-CoA synthetase activity by site-specific lysine acetylation and highlights the potential regulation of fatty acid metabolism by lysine actetylation in the plastid of the diatom Phaeodactylum.4
Purpose
Breast cancer (BC), with varying histopathology, biology and response to systemic treatment, is the second leading cause of cancer-related mortality. Previous studies have inferred that the expression of mitochondrial ribosomal proteins (MRPs) is possibly related to the occurrence/progression of BC. MRPL13 might be one of the potential MRP candidates that are involved in BC tumorigenesis, but its role in BC has rarely been reported. The purpose of the current study was to evaluate the prognostic significance of MRPL13, as well as to explore its potential biological functions in BC.
Materials and Methods
A series of bioinformatic and statistical methods were adopted to assess the MRPL13 expression profile, its relationship with clinicopathological characteristics, copy number variation (CNV), impact on clinical outcomes and relevant functions. All the results are analysed by 1097 BC patients collected from The Cancer Genome Atlas (TCGA) dataset and 52 clinical samples for immunohistochemistry (IHC) assay.
Results
The results demonstrated that the expression of MRPL13 in BC tissues was remarkably elevated than that in normal breast tissues. In addition, the Kaplan-Meier curves and Cox model indicated that patients with high MRPL13 expression were connected to a worse prognosis, heralding the independent prognostic value of this protein in BC. Moreover, an enrichment analysis showed that MRPL13 was mainly involved in cell cycle/division-related, RNA processing (degradation/splicing), MYC targets and the MTORC1 pathways. In addition, RNA interference (RNAi)-mediated MRPL13 silencing remarkedly inhibited proliferation and migration as well as the expression of EMT-related genes of BC cells in vitro. Mechanistically, attenuation of MRPL13 significantly suppressed the phosphorylation of AKT and mTOR, which could be partially abolished by 740Y-P (a PI3K agonist).
Conclusion
Our results provide evidence for the first time that increased MRPL13 expression correlates with adverse clinicopathological variables and unfavorable clinical outcomes of BC patients. Knockdown of MRPL13 restrains the proliferation and migration potential and EMT process of BC through inhibiting PI3K/AKT/mTOR signaling pathway.
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