Over-expression of Hsp83 in grossly depletedhsrωlncRNA background causes synthetic lethality andl(2)glphenocopy inDrosophila

Abstract

We examined interactions between Hsp83 and hsrω lncRNAs in hsrω 66 Hsp90GFP homozygotes, which almost completely lack hsrω lncRNAs but over-express Hsp83. All +/+; hsrω 66 Hsp90GFP progeny died before third instar. Rare Sp/CyO; hsrω 66 Hsp90GFP reached third instar stage but phenocopied l(2)gl mutants, dying after prolonged larval life, becoming progressively bulbous and transparent with enlarged brain. Additionally, ventral ganglia were elongated. However, hsrω 66 Hsp90GFP/TM6B heterozygotes, carrying +/+ or Sp/CyO second chromosomes, developed normally. Total RNA sequencing (+/+, +/+; hsrω 66 /hsrω 66 , Sp/CyO; hsrω 66 /hsrω 66 , +/+; Hsp90GFP/Hsp90GFP, and Sp/CyO; hsrω 66 Hsp90GFP/hsrω 66 Hsp90GFP late third instar larvae) revealed similar effects on many genes in hsrω 66 and Hsp90GFP homozygotes. Besides additive effect on many of them, numerous additional genes were affected in Sp/CyO; hsrω 66 Hsp90GFP larvae, with l(2)gl and several genes regulating CNS being highly down-regulated in surviving Sp/CyO; hsrω 66 Hsp90GFP larvae, but not in hsrω 66 or Hsp90GFP single mutants. Hsp83 binds at these gene promoters. Several omega speckle associated hnRNPs too may bind with these genes and transcripts. Hsp83-hnRNP interactions are also known. Thus, elevated Hsp83 in altered hnRNP distribution and dynamics, following absence of hsrω lncRNAs and omega speckles, background can severely perturb regulatory circuits with unexpected consequences, including down-regulation of tumor suppressor gene like l(2)gl. 0 1 5

Activated Ras/JNK driven Dilp8 in imaginal discs adversely affects organismal homeostasis during early pupal stage in Drosophila, a new checkpoint for development

“…The upregulated groups of genes (Table ) in sev‐GAL4 > UAS‐Ras1 V12 hsrω‐RNAi pupae included, among many others, those associated with stress responses, cell and tissue death pathways, autophagy, toll signaling, innate immune system, and so forth. Some of these seem to be primarily due to activated Ras or altered hsrω expression since the Ras/MAPK pathway is known to regulate immune response while the hsrω transcripts have roles in stress responses, cell death, and several other pathways . However, beside the predicted upregulation of G‐protein coupled signal transduction pathway following ectopic expression of activated Ras, a significant increase in expression of several JNK pathway genes was also noted (Tables and ).…”

“…Earlier studies in our and other labs have shown that the hsrω lncRNA gene in Drosophila melanogaster regulates many cellular regulatory pathways through diverse mechanisms, of which the modulation of dynamics of heterogeneous nuclear RNA binding proteins (hnRNPs) and certain other RNA binding proteins seems to be a major component . We had earlier found a genetic interaction between Hsp83, Ras signaling pathways and the hsrω lncRNAs .…”

“…Some of these seem to be primarily due to activated Ras or altered hsrω expression since the Ras/MAPK pathway is known to regulate immune response 32,33 while the hsrω transcripts have roles in stress responses, cell death, and several other pathways. 5,8,11,34,35 However, beside the predicted upregulation of G-protein coupled signal transduction pathway following ectopic expression of activated Ras, a significant increase in expression of several JNK pathway genes was also noted (Tables 2 and 3).…”

“…[1][2][3][4] Earlier studies in our and other labs have shown that the hsrω lncRNA gene in Drosophila melanogaster regulates many cellular regulatory pathways through diverse mechanisms, of which the modulation of dynamics of heterogeneous nuclear RNA binding proteins (hnRNPs) and certain other RNA binding proteins seems to be a major component. [5][6][7][8] We had earlier found a genetic interaction between Hsp83, Ras signaling pathways and the hsrω lncRNAs. 9,10 Confirming these earlier studies, more recently we found that the ectopically induced high level of Ras signaling cascade was further enhanced when hsrω lncRNA levels were simultaneously downregulated in eye discs of Drosophila third instar larvae.…”

Activated Ras/JNK driven Dilp8 in imaginal discs adversely affects organismal homeostasis during early pupal stage inDrosophila, a new checkpoint for development

“…The up-regulated groups of genes (Table 2) in sev-GAL4>UAS-Ras1 V12 hsrω-RNAi pupae included, among many others, those associated with stress responses, cell and tissue death pathways, autophagy, toll signaling, innate immune system etc. Some of these seem to be primarily due to activated Ras or altered hsrω expression since the Ras/MAPK pathway is known to regulate immune response (Ragab et al, 2011;Hauling et al, 2014) while the hsrω transcripts have roles in stress responses, cell death and several other pathways (Mallik and Lakhotia, 2009a;Lakhotia, 2011;Lakhotia, 2016;Ray et al, 2019a;Ray et al, 2019b). However, beside the predicted up-regulation of G-protein coupled signal transduction pathway following ectopic expression of activated Ras, a significant increase in expression of several JNK pathway genes was also noted (Tables 2 and 3).…”