Ubiquitin-specific peptidase 10 (USP10) stabilizes both tumor suppressors and oncogenes in a context-dependent manner. However, the nature of USP10's role in non-small cell lung cancer (NSCLC) remains unclear. By analyzing The Cancer Genome Atlas (TCGA) database, we have shown that high levels of USP10 are associated with poor overall survival in NSCLC with mutant p53, but not with wild-type p53. Consistently, genetic depletion or pharmacological inhibition of USP10 dramatically reduces the growth of lung cancer xenografts lacking wild-type p53 and sensitizes them to cisplatin. Mechanistically, USP10 interacts with, deubiquitinates, and stabilizes oncogenic protein histone deacetylase 6 (HDAC6). Furthermore, reintroducing either USP10 or HDAC6 into a USP10-knockdown NSCLC H1299 cell line with null-p53 renders cisplatin resistance. This result suggests the existence of a "USP10-HDAC6-cisplatin resistance" axis. Clinically, we have found a positive correlation between USP10 and HDAC6 expression in a cohort of NSCLC patient samples. Moreover, we have shown that high levels of USP10 mRNA correlate with poor overall survival in a cohort of advanced NSCLC patients who received platinum-based chemotherapy. Overall, our studies suggest that USP10 could be a potential biomarker for predicting patient response to platinum, and that targeting USP10 could sensitize lung cancer patients lacking wild-type p53 to platinum-based therapy.

Histone deacetylase 6 (HDAC6), a class IIb HDAC, plays an important role in many biological and pathological processes. Previously, we found that ERK1, a downstream kinase in the MAPK signaling pathway, phosphorylates HDAC6, thereby increasing HDAC6-mediated deacetylation of α-tubulin. However, whether HDAC6 reciprocally modulates ERK1 activity is unknown. Here, we report that both ERK1 and 2 are acetylated and that HDAC6 promotes ERK1 activity via deacetylation. Briefly, we found that both ERK1 and 2 physically interact with HDAC6. Endogenous ERK1/2 acetylation levels increased upon treatment with a pan-HDAC inhibitor, an HDAC6-specific inhibitor or depletion of HDAC6, suggesting that HDAC6 deacetylates ERK1/2. We also noted that the acetyltransferases CBP and p300 both can acetylate ERK1/2. Acetylated ERK1 exhibits reduced enzymatic activity toward the transcription factor ELK1, a well-known ERK1 substrate. Furthermore, mass spectrometry analysis indicated Lys-72 as an acetylation site in the ERK1 N-terminus, adjacent to Lys-71, which binds to ATP, suggesting that acetylation status of Lys-72 may affect ERK1 ATP binding. Interestingly, an acetylation-mimicking ERK1 mutant (K72Q) exhibited less phosphorylation than the WT enzyme and a deacetylationmimicking mutant (K72R). Of note, the K72Q mutant displayed decreased enzymatic activity in an in vitro kinase assay and in a cellular luciferase assay compared with the WT and K72R mutant. Taken together, our findings suggest that HDAC6 stimulates ERK1 activity. Along with our previous report that ERK1 promotes HDAC6 activity, we propose that HDAC6 and ERK1 may form a positive feedforward loop, which might play a role in cancer.Histone deacetylases (HDACs) and histone acetyltransferases (HATs) are the enzymes that regulate core histones and non-histone proteins by deacetylation and acetylation, respectively (1). HATs acetylate proteins via adding acetyl groups to lysine residues, while HDACs catalyze a reverse reaction by removing the acetyl group from lysine residues. Up to now, a total of 18 HDACs are identified in humans and grouped HDAC6 deacetylates ERK12 into four classes based on their sequence similarity to yeast orthologs (2). Class I HDACs are homologous to yeast reduced potassium dependency 3 (Rpd3) and include HDACs 1, 2, 3 and 8. Class II HDACs are homologous to yeast histone deacetylase 1 (HdaI) and are further divided into class IIa and class IIb. Class IIa contains HDACs 4, 5, 7 and 9, and class IIb includes HDACs 6 and 10. HDAC11 is the only member in class IV. The deacetylase activity of HDAC classes I, II and IV is zinc-dependent. Class III HDACs, also knowns as sirtuins, are homologous to yeast silent information regulator 2 (Sir2), and the deacetylase activity of this class is oxidized nicotinamide adenine dinucleotide (NAD + )-dependent. HDAC6 belongs to class IIb HDACs. Its structure is quite unique among all HDACs, in that it contains two functional deacetylase domains in tandem and a zinc finger domain in the C-terminus (2,3). HDAC6...

Human methyltransferase-like (METTL) proteins transfer methyl groups to nucleic acids, proteins, lipids, and other small molecules, subsequently playing important roles in various cellular processes. In this study, we performed integrated genomic, transcriptomic, proteomic, and clinicopathological analyses of 34 METTLs in a large cohort of primary tumor and cell line data. We identified a subset of METTL genes, notably METTL1, METTL7B, and NTMT1, with high frequencies of genomic amplification and/or up-regulation at both the mRNA and protein levels in a spectrum of human cancers. Higher METTL1 expression was associated with high-grade tumors and poor disease prognosis. Loss-of-function analysis in tumor cell lines indicated the biological importance of METTL1, an m7G methyltransferase, in cancer cell growth and survival. Furthermore, functional annotation and pathway analysis of METTL1-associated proteins revealed that, in addition to the METTL1 cofactor WDR4, RNA regulators and DNA packaging complexes may be functionally interconnected with METTL1 in human cancer. Finally, we generated a crystal structure model of the METTL1–WDR4 heterodimeric complex that might aid in understanding the key functional residues. Our results provide new information for further functional study of some METTL alterations in human cancer and might lead to the development of small inhibitors that target cancer-promoting METTLs.