[Biological function and clinical significance of long non-coding RNA LINC00342 in head and neck squamous carcinoma].

Objective: To investigate the relationship between the long-non-coding RNA LINC00342 expression and the clinicopathological parameters of head and neck squamous cell carcinoma (HNSCC) and the biological function of LINC00342 in HNSCC cells. Methods: The expression level of LINC00342 in the HNSCC was analyzed using transcriptome sequencing data from TCGA (The Cancer Genome Atlas) database, and the expressions of LINC00342 in laryngeal squamous cell carcinoma tissues (LSCC) of 27 patients in the First Hospital of Shanxi Medical University were detected by transcriptome sequencing. The expression levels of LINC00342 in human embryonic lung diploid cells 2BS, HNSCC cell lines FD-LSC-1, CAL-27 and Detroit562 were determined by real-time quantitative polymerase chain reaction (qPCR). RNAi (RNA interference) was used for LINC00342 knockdown in HNSCC cell lines, and the changes of malignant phenotype in the tumor cells after LINC00342 knockdown were examined by cell counting kit-8 (CCK-8), colony formation, flow cytometry, transwell invasion and migration assays. Bioinformatics analysis was performed to construct a LINC00342-centered competing endogenous RNA (ceRNA) regulatory network, and GO (Gene Ontology) enrichment analysis was performed. Statistical analysis and graphing were performed using SPSS 25.0 software and GraphPad Prism 6 software. Results: Mean LINC00342 levels in HNSCC tissues and TCGA database were higher than that in normal control tissues, but with no significantly statistical difference (P=0.522). LINC00342 expression levels were positively correlated with cervical lymph node metastasis and pathological grade in patients with HNSCC, with higher expression in male patients than in female patients (P<0.05). Transcriptome sequencing analysis showed that mean expression level of LINC00342 in LSCC tissues of 27 patients was significantly higher than that in the paired adjacent normal mucosa tissues (t=1.56, P=0.036). LINC00342 expression was significantly upregulated in HNSCC cell lines FD-LSC-1, CAL-27 and Detroit562 (t-values of -12.17, -23.26 and -388.57, respectively; all P<0.001). Knockdown of LINC00342 by transfecting si-LINC00342-1 and si-LINC00342-2 inhibited HNSCC cell proliferation (t-values of 8.95 and 4.84, 2.70 and 5.55, 2.02 and 3.70, respectively), colony formation (t-values of 6.66 and 6.17, 7.38 and 11.65, 4.90 and 5.79, respectively), migration (t-values of 8.21 and 7.19, 5.76 and 6.46, 6.28 and 9.92, respectively) and invasion abilities (t-values of 9.29 and 10.25, 11.30 and 11.36, 8.02 and 8.66, respectively), but promoting apoptosis in cell lines FD-LSC-1 and CAL-27 (t-values of -2.21 and -5.83, -3.05 and -5.25 respectively) (all P-values<0.05). The LINC00342-centered ceRNA network consists of 10 downregulated microRNA and 647 upregulated mRNA nodes. GO analysis results indicated that LINC00342-regulated mRNAs were enriched in 22 biological processes, 32 molecular functions, and 12 cellular components. Conclusion: High level of LINC00342 is associated with the malignant progression of HNSCC. LINC00342 promotes the proliferation, migration, invasion, and antagonizes apoptosis of HNSCC cells, which serves as a potential molecular marker in HNSCC.

Structural analysis of the Neurospora mitochondrial large rRNA intron and construction of a mini-intron that shows protein-dependent splicing.

The gene encoding the Neurospora mitochondrial large rRNA contains a single group I intron of 2.3 kilobases that is not self-splicing in vitro. We showed previously that the splicing of this intron in vivo and in vitro is dependent on the Neurospora cyt-18 protein, mitochondrial tyrosyl-tRNA synthetase. In the present work, we carried out further structural analysis of the intron and constructed mutant derivatives of it in order to identify features that are either required for splicing or prevent it from self-splicing. Previous studies showed that the intron contains a large hairpin structure near the 5' splice site. By mapping RNase III cleavage sites, we identified this hairpin structure as an extended P2 stem. We construct a mini-intron of 388 nucleotides by deleting the 426-amino acid intron open reading frame, most of the 5' intron hairpin, and all of L8. This mini-intron shows the same protein-dependent splicing as the full length intron, but is still not self-splicing. Further deletions, which remove all of P2 or all or part of P4, P6, P7, or P9, inactivate splicing, suggesting that an intact group I intron core structure is required. Strengthening the P1, P10, or P9.0 pairings did not enable the mini-intron to self-splice. Our findings indicate that the inability of the mitochondrial large rRNA intron to self-splice reflects deficiency of a structure or activity required for cleavage at the 5' splice site, either in the intron core itself or in the interaction between the core and the P1 stem.