Zhen Qin

Metastasis is the dominant cause of patient death in small-cell lung cancer (SCLC), and a better understanding of the molecular mechanisms underlying SCLC metastasis may potentially improve clinical treatment. Through genome-scale screening for key regulators of mouse Rb1-/- Trp53-/- SCLC metastasis using the pooled CRISPR/Cas9 library, we identified Cullin5 (CUL5) and suppressor of cytokine signaling 3 (SOCS3), two components of the Cullin-RING E3 ubiquitin ligase complex, as top candidates. Mechanistically, the deficiency of CUL5 or SOCS3 disrupted the functional formation of the E3 ligase complex and prevented the degradation of integrin β1, which stabilized integrin β1 and activated downstream focal adhesion kinase/SRC (FAK/SRC) signaling and eventually drove SCLC metastasis. Low expression levels of CUL5 and SOCS3 were significantly associated with high integrin β1 levels and poor prognosis in a large cohort of 128 clinical patients with SCLC. Moreover, the CUL5-deficient SCLCs were vulnerable to the treatment of the FDA-approved SRC inhibitor dasatinib. Collectively, this work identifies the essential role of CUL5- and SOCS3-mediated integrin β1 turnover in controlling SCLC metastasis, which might have therapeutic implications.

Significance Tumor suppressor genes (TSGs) play important roles in lung cancer initiation, progression, and even metastasis. Here, we take advantage of the clustered regularly interspaced short palindromic repeats/Cas9-mediated screening in vivo technique to identify multiple tumor suppressor genes contributing to lung cancer malignant progression. Using genetically engineered mouse models, we further confirm the tumor-suppressive role of epigenetic regulator UTX and provide therapeutic implications for UTX-deficient lung tumors. Thus, our work provides a systematic screening of TSGs in vivo and demonstrates UTX functions as the important epigenetic regulator in lung tumorigenesis.

Neuronal differentiation is tightly regulated by a variety of factors. In a search for neuron-specific genes, we identified a highly conserved novel zinc finger protein, ZNF536. We observed that ZNF536 is most abundant in the brain and, in particular, is expressed in the developing central nervous system and dorsal root ganglia and localized in the cerebral cortex, hippocampus, and hypothalamic area. During neuronal differentiation of P19 cells induced by retinoic acid (RA), ZNF536 expression is increased at an early stage, and it is maintained at a constant level in later stages. Overexpression of ZNF536 results in an inhibition of RA-induced neuronal differentiation, while depletion or mutation of the ZNF536 gene results in an enhancement of differentiation. We further demonstrated that ZNF536 inhibits expression of neuron-specific marker genes, possibly through the inhibition of RA response element-mediated transcriptional activity, as overexpression of RA receptor alpha can rescue the inhibitory role of ZNF536 in neuronal differentiation and neuron-specific gene expression. Our studies have identified a novel zinc finger protein that negatively regulates neuron differentiation.

Heat stress greatly threatens crop production. Plants have evolved multiple adaptive mechanisms, including alternative splicing, that allow them to withstand this stress. However, how alternative splicing contributes to heat stress responses in wheat (Triticum aestivum) is unclear. We reveal that the heat shock transcription factor gene TaHSFA6e is alternatively spliced in response to heat stress. TaHSFA6e generates two major functional transcripts: TaHSFA6e-II and TaHSFA6e-III. TaHSFA6e-III enhances the transcriptional activity of three downstream heat shock protein 70 (TaHSP70) genes to a greater extent than does TaHSFA6e-II. Further investigation reveals that the enhanced transcriptional activity of TaHSFA6e-III is due to a 14-amino acid peptide at its C-terminus, which arises from alternative splicing and is predicted to form an amphipathic helix. Results show that knockout of TaHSFA6e or TaHSP70s increases heat sensitivity in wheat. Moreover, TaHSP70s are localized in stress granule following exposure to heat stress and are involved in regulating stress granule disassembly and translation re-initiation upon stress relief. Polysome profiling analysis confirms that the translational efficiency of stress granule stored mRNAs is lower at the recovery stage in Tahsp70s mutants than in the wild types. Our finding provides insight into the molecular mechanisms by which alternative splicing improves the thermotolerance in wheat.