Protein synthesis rates in Drosophila associate with levels of the hsr-omega nuclear transcript

Abstract

Transcripts of the Drosophila hsr-omega gene are known to interact with RNA processing factors and ribosomes and are postulated to aid in co-ordinating nuclear and cytoplasmic activities particularly in stressed cells. However, the significance of these interactions for physiological processes and in turn for whole-organism fitness remains an open question. Because hsr-omega's cellular expression characteristics suggest it may influence protein synthesis, and because both genotypic and expression variation of hsr-omega have been associated with thermotolerance, we characterised 30 lines for variation in the rates of protein synthesis, measured in ovarian tissues, both before and after a mild heat shock, and for basal levels of the two main hsr-omega transcripts, omega-n and omega-c. As expected, the mild heat shock reduced protein synthesis rates. Large variation occurred among lines in levels of omega-n which was negatively associated with rates of basal protein synthesis-a result that supports the model for the cellular function of omega-n. Furthermore, omega-n levels were associated with hsr-omega genotype of the line parents. Little variation occurred among lines for omega-c levels and no associations were detected with protein synthesis or genotype. Since protein synthesis is a fundamental process for growth and development, we characterised the lines for several life-history traits; however, no associations with protein synthesis, omega-n or omega-c levels were detected. Our results are consistent with the idea that natural variation in hsr-omega expression influence rates of protein synthesis in this species.

The Developmentally Active and Stress-Inducible Noncoding hsrω Gene Is a Novel Regulator of Apoptosis in Drosophila

“…In this context, it is interesting to note that under conditions of global inhibition of cellular protein synthesis, the level of the small cytoplasmic hsrv-c transcript is enhanced (Bendena et al 1989). It has also been reported more recently that the quantity and quality of hsrv transcripts affect levels of protein synthesis in flies ( Johnson et al 2009). Such possible effects of hsrv transcripts on the cellular translation apparatus may be yet another mechanism that may modulate cellular levels of DIAP1 in Rpr-or Grim-expressing cells.…”

Transcripts from the Drosophila heat-shock gene hsr-omega influence rates of protein synthesis but hardly affect resistance to heat knockdown

“…Quantification of hsr-omega transcript levels Levels of omega-n and omega-c were estimated by real time RT-PCR as previously described (Collinge et al 2008;Johnson et al 2009a). Transcript specificity was assured by primer placement; for omega-n both primers were downstream of the full omega-c template (and upstream of the repeat region), and for omega-c the forward primer spanned the intron splice junction while the reverse primer was close-by (near the 5 0 end of the omega-c template, as depicted in Johnson et al 2009a).…”

“…Transcript specificity was assured by primer placement; for omega-n both primers were downstream of the full omega-c template (and upstream of the repeat region), and for omega-c the forward primer spanned the intron splice junction while the reverse primer was close-by (near the 5 0 end of the omega-c template, as depicted in Johnson et al 2009a). Three replicate RNA extractions were made for each line for both basal and heatshocked treatments.…”

“…Protein synthesis rates were assessed by measuring the amount of 35 S-methionine incorporated into dissected ovarian tissue in 1 h, as previously described (Johnson et al 2009a). For each line (w 1118 and lines homozygous for 29, EP1328 and 56) rearing occurred in parallel at 25°C at controlled densities in five separate cultures vials in which adults were allowed to mate until 5-7 days old.…”

“…Omega-n regulates availability of nuclear factors known primarily to be involved in pre-mRNA processing (Lakhotia et al 1999;Prasanth et al 2000). Thus, we might expect lines differing in the levels of the nuclear transcript to have altered levels of general protein synthesis, and recent evidence supports this idea (Johnson et al 2009a).…”