Depletion of ribosomal protein L8 impairs Drosophila development and is associated with apoptosis

Abstract

Ribosomal protein L8 is a component of the 60S subunit of the ribosome and is involved in protein synthesis but its role in Drosophila development is not well understood. We depleted L8 through RNA interference (RNAi) to examine its effects on fly development both in vivo and in vitro. The results demonstrated that L8 RNAi caused embryonic or first-larval lethality, delay of larval development, defects in eye and wing morphology, and dramatically reduced the number of S2 cells. This indicated that L8 plays a crucial role in Drosophila development. Acridine orange staining of the wing discs showed that apoptosis occurred when L8 was depleted, indicating that depletion of L8 is tightly connected to apoptosis. RT-PCR analyses of the transcription level of genes that are known to be key factors in apoptosis (p53, hid, reaper, dark, Dcp-1) and cell cycle regulation (cdc45, MCM3, cyclin B, incenp) in L8-deficient S2 cells, were consistent with their role in apoptosis induction and cell cycle arrest. These results indicate that depletion of L8 strongly impairs Drosophila development, and that this depletion is associated with cell proliferation arrest and apoptosis, in which p53 may play a central role.

The role of ribosomal proteins in the regulation of cell proliferation, tumorigenesis, and genomic integrity

“…Activated p53 then transactivates its downstream targets to induce growth arrest and apoptosis to block tumorigenesis. (Adilakshmi and Laine, 2002;Bai et al, 2014;Barlow et al, 2010a;He and Sun, 2007;Jang et al, 2012a;Jeon et al, 2008;Khanna et al, 2003;Li et al, 2010;Naora et al, 1998;Neumann and Krawinkel, 1997;Russo et al, 2013;Takagi et al, 2005;Wu et al, 2012;Yang et al, 2012;Zhu et al, 2009) Cell cycle S3, S5, S6, S7, S14, S15, S19, S20, S25, S26, S27, S27L, S27a, L3, L5, L6, L7, L11, L13, L23, L26, L31, L34, L37, L41 (Cui et al, 2014;Daftuar et al, 2013;Dai et al, , 2007bGao et al, 2013;Gou et al, 2010;Iadevaia et al, 2010;Kobayashi et al, 2006;Maruyama et al, 2014;Matragkou et al, 2008;Moorthamer and Chaudhuri, 1999;Neumann and Krawinkel, 1997;Russo et al, 2013;Sun et al, 2011;Takagi et al, 2005;Wang et al, 2011a;Wanzel et al, 2008;Xiong et al, 2011;Zhang et al, 2013Zhang et al, , 2015Zhou et al, 2013a) Cell proliferation S6, S9, S13, S14, S15a, S24, S27, L6, L8, L11, L15, L17, L26, L29, L31, L34, L36a (Dai et al, 2007a;Gou et al, 2010Kim et al, 2004;Li et al, 2010…”

“…Remarkably, many RPs, including S3, S7, S14, S15, S20, S25, S26, S27, S27a, S27L, L5, L6, L11, L23, L26, and L37, were reported to activate p53 and to induce p53-dependent cell cycle arrest as well as apoptosis upon ribosomal stress (Cui et al, 2014;Daftuar et al, 2013;Dai et al, 2007bGou et al, 2010;Jang et al, 2012b;Sun et al, 2011;Takagi et al, 2005;Xiong et al, 2011;Zhang et al, 2013;Zhou et al, 2013a;Zhu et al, 2009). This is mainly achieved by the binding of RPs to MDM2, which inhibits MDM2-mediated p53 ubiquitylation and degradation, leading to p53 activation (Cui et al, 2014;Daftuar et al, 2013;Dai et al, 2007bSun et al, 2011;Takagi et al, 2005;Xiong et al, 2011;Zhang et al, 2013;Zhu et al, 2009) (Figure 1B).…”

Ribosomal Proteins and Human Diseases: Pathogenesis, Molecular Mechanisms, and Therapeutic Implications

“…In addition to rRNA, p53 also regulates the transcription of RP genes . For instance, p53 directly induces the expression of an RP, S27L,…”

“…Upon NGF (nerve growth factor) stimulation, Akt interacts with and phosphorylates S3 (Thr70), which disturbs its association with E2F1 and enhances S3 nuclear translocation, resulting in increased DNA repair activity and sustained neuronal survival . On the other hand, genotoxic stress induces the translocation of S3 to damage sites through ERK‐mediated phosphorylation of S3 at Thr42 . In addition, the phosphorylation of S3 mediates radioresistance in nonsmall cell lung cancer (NSCLC) cells .…”

“…The deletion of miR‐145/146a is responsible for other hematological phenotypes, such as thrombocytosis and megakaryocytic defects . The loss of S14 induces and activates p53, leading to p21‐mediated cell cycle arrest and destruction of erythroid progenitor cells , …”