Dissecting the Nuclear Import of the Ribosomal Protein Rps2 (uS5).

The ribosome is assembled in a complex process mainly taking place in the nucleus. Consequently, newly synthesized ribosomal proteins have to travel from the cytoplasm into the nucleus, where they are incorporated into nascent ribosomal subunits. In this study, we set out to investigate the mechanism mediating nuclear import of the small subunit ribosomal protein Rps2. We demonstrate that an internal region in Rps2, ranging from amino acids 76 to 145, is sufficient to target a 3xyEGFP reporter to the nucleus. The importin-ß Pse1 interacts with this Rps2 region and is involved in its import, with Rps2 residues arginine 95, arginine 97, and lysine 99 being important determinants for both Pse1 binding and nuclear localization. Moreover, our data reveal a second import mechanism involving the N-terminal region of Rps2, which depends on the presence of basic residues within amino acids 10 to 28. This Rps2 segment overlaps with the binding site of the dedicated chaperone Tsr4; however, the nuclear import of Rps2 via the internal as well as the N-terminal nuclear-targeting element does not depend on Tsr4. Taken together, our study has unveiled hitherto undescribed nuclear import signals, showcasing the versatility of the mechanisms coordinating the nuclear import of ribosomal proteins.

Global analysis of protein arginine methylation.

Quantitative information about the levels and dynamics of post-translational modifications (PTMs) is critical for an understanding of cellular functions. Protein arginine methylation (ArgMet) is an important subclass of PTMs and is involved in a plethora of (patho)physiological processes. However, because of the lack of methods for global analysis of ArgMet, the link between ArgMet levels, dynamics, and (patho)physiology remains largely unknown. We utilized the high sensitivity and robustness of nuclear magnetic resonance (NMR) spectroscopy to develop a general method for the quantification of global protein ArgMet. Our NMR-based approach enables the detection of protein ArgMet in purified proteins, cells, organoids, and mouse tissues. We demonstrate that the process of ArgMet is a highly prevalent PTM and can be modulated by small-molecule inhibitors and metabolites and changes in cancer and during aging. Thus, our approach enables us to address a wide range of biological questions related to ArgMet in health and disease.

MicroRNA-182-5p regulates hedgehog signaling pathway and chemosensitivity of cisplatin-resistant lung adenocarcinoma cells via targeting GLI2.

Lung cancer is one of the deadliest cancers worldwide. Late diagnosis at an advanced, inoperable stage makes chemotherapy a treatment of choice, yet, with low response rates. The hedgehog signaling pathway (HHSP) is often reactivated in cancer. We identified miR-182-5p as a regulator of GLI2, a transcriptional regulator of the HHSP, and explored the role of the miR-182-5p/GLI2 axis in carcinogenesis and cisplatin resistance of lung adenocarcinoma (LADC). Expression of miRNAs and target genes was analyzed by RT-qPCR, expression of the GLI-protein family in LADC and adjacent lung tissue (n = 27 pairs) by immunohistochemistry. MiR-182-5p was manipulated, and data were generated by immunoblotting, immunofluorescence, apoptosis, proliferation/viability, dual-luciferase-, and colony forming assays. MiR-182-5p was down-regulated in cisplatin-resistant LADC cells and directly targeted GLI2. Interference with miR-182-5p or GLI2 silencing resulted in modulation of cell proliferation, clonogenic potential, and cisplatin-sensitivity. HHSP was markedly reactivated in LADC tissue compared to adjacent non-malignant lung tissue. Our results indicate that the miR-182-5p/GLI2 axis modulates tumorigenesis and cisplatin-resistance in LADC cells, by influencing the HHSP. Therefore, this axis might be considered as a potential biomarker and future therapeutic target in LADC patients.