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AIM: To investigate the role of Ywhab in the growth of mouse B-cell lymphoma, and to explore the potential underlying mechanisms. METHODS : The correlation between Ywhab and human diffuse large B-cell lymphoma (DLBCL) was investigated by bioinformatics analysis. Infection with retroviral vector was performed to establish stable mouse B-cell lymphoma 38B9 cell line with overexpression of Ywhab gene, which was verified by RT-qPCR and Western blot. The impact of Ywhab overexpression on 38B9 cell growth both in vitro and in vivo was detected by cell counting, CCK-8 assay, and subcutaneous tumor loading experiments. The expression of apoptosis-related proteins was detected by RT-qPCR and Western blot. Co-immunoprecipitation combined with mass spectrometry (CoIP-MS) was employed to search for proteins specifically binding to Ywhab gene product 14-3-3β, which was confirmed by Western blot and molecular docking analysis. RESULTS: The Ywhab gene exhibited low expression in DLBCL, which was correlated with poor clinical prognosis of DLBCL patients. Compared with normal mouse bone marrow B cells, Ywhab expression was low in 38B9 cells. Overexpression of Ywhab induced apoptosis of 38B9 cells both in vitro and in vivo, promoted the expression of pro-apoptotic proteins Puma, Noxa and Bax at both mRNA and protein levels, and inhibited the mRNA and protein expression of anti-apoptotic protein Bcl2 (P<0. 05). The 14-3-3β protein specifically bound to Hsp90aa1 and reduced Hsp90aa1 protein levels, thereby suppressing the growth of 38B9 cells. CONCLUSION: Ywhab promotes the apoptosis of B-cell lymphoma cells by binding to Hsp90aa1 and thereby inhibiting the function of Hsp90aa1. [ABSTRACT FROM AUTHOR]

Myc is a pivotal protooncogenic transcription factor that contributes to the development of almost all Burkitt's lymphomas and about one-third of diffuse large B-cell lymphomas. How B-cells sustain their uncontrolled proliferation due to high Myc is not yet well defined. Here, we found that Myc trans-represses the expression of murine LAPTM5, a gene coding a lysosome-associated protein, by binding to two E-boxes in the LAPTM5 promoter. While the product of intact mRNA (CDS+3′UTR) of LAPTM5 failed to suppress the growth of B-lymphomas, either the protein coded by coding sequence (CDS) itself or the non-coding 3′-untranslated region (3′UTR) mRNA was able to inhibit the growth of B-lymphomas. Moreover, Myc trans-activated miR-17-3p, which promoted tumor growth. Strikingly, LAPTM5 3′UTR contains 11 miR-17-3p-binding sites through which the LAPTM5 protein synthesis was inhibited. The functional interplay between low LAPTM5 mRNA and high miR-17-3p due to high Myc in B-lymphomas leads to further dampening of tumor-suppressive LAPTM5 protein, which promotes tumor progression. Our results indicate that Myc inhibits LAPTM5 expression in B-lymphoma cells by transcriptional and post-transcriptional modifications. [ABSTRACT FROM AUTHOR]