Over-expression of Hsp83 in grossly depleted hsrω lncRNA background causes synthetic lethality and l(2)gl phenocopy in Drosophila

Abstract

AbstractWe examined interactions between Hsp83 and hsrω lncRNAs in hsrω66Hsp90GFP homozygotes, which almost completely lack hsrω lncRNAs but over-express Hsp83. All +/+; hsrω66Hsp90GFP progeny died before third instar. Rare Sp/CyO; hsrω66Hsp90GFP 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, hsrω66Hsp90GFP/TM6B heterozygotes, carrying +/+ or Sp/CyO second chromosomes, developed normally. Total RNA sequencing (+/+, +/+; hsrω66/hsrω66, Sp/CyO; hsrω66/hsrω66, +/+; Hsp90GFP/Hsp90GFP, and Sp/CyO; hsrω66Hsp90GFP/hsrω66Hsp90GFP late third instar larvae) revealed similar effects on many genes in hsrω66 and Hsp90GFP homozygotes. Besides additive effect on many of them, numerous additional genes were affected in Sp/CyO; hsrω66Hsp90GFP larvae, with l(2)gl and several genes regulating CNS being highly down-regulated in surviving Sp/CyO; hsrω66Hsp90GFP larvae, but not in hsrω66 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.