The 5′-3′ exoribonuclease Pacman (Xrn1) regulates expression of the heat shock protein Hsp67Bc and the microRNAmiR-277–3pinDrosophilawing imaginal discs

Abstract

Pacman/Xrn1 is a highly conserved exoribonuclease known to play a critical role in gene regulatory events such as control of mRNA stability, RNA interference and regulation via miRNAs. Although Pacman has been well studied in Drosophila tissue culture cells, the biologically relevant cellular pathways controlled by Pacman in natural tissues are unknown. This study shows that a hypomorphic mutation in pacman (pcm5) results in smaller wing imaginal discs. These tissues, found in the larva, are known to grow and differentiate to form wing and thorax structures in the adult fly. Using microarray analysis, followed by quantitative RT-PCR, we show that eight mRNAs were increased in level by > 2-fold in the pcm5 mutant wing discs compared with the control. The levels of pre-mRNAs were tested for five of these mRNAs; four did not increase in the pcm5 mutant, showing that they are regulated at the post-transcriptional level and, therefore, could be directly affected by Pacman. These transcripts include one that encodes the heat shock protein Hsp67Bc, which is upregulated 11.9-fold at the post-transcriptional level and 2.3-fold at the protein level. One miRNA, miR-277-3p, is 5.6-fold downregulated at the post-transcriptional level in mutant discs, suggesting that Pacman affects its processing in this tissue. Together, these data show that a relatively small number of mRNAs and miRNAs substantially change in abundance in pacman mutant wing imaginal discs. Since Hsp67Bc is known to regulate autophagy and protein synthesis, it is possible that Pacman may control the growth of wing imaginal discs by regulating these processes.

The 3'-5' exoribonuclease Dis3 regulates the expression of specific microRNAs inDrosophilawing imaginal discs

“…A total of 109 mature miRNAs were detected (with >1 read per sample), with the most abundant miRNA, miR-9a-5p, roughly 12,000-fold more abundant than the levels of the least abundant miRNA reliably detected (miR-307a-3p). These results are similar to that of our previous study using microarrays 5 in that the highly expressed miRNAs according to microarray analysis are also found to be most abundant in the more sensitive RNA-seq analysis. This analysis also confirms that the miRNAs that change 2-fold in levels upon Dis3 depletion are also those that are normally expressed at low levels in wing imaginal discs, suggesting that Dis3 plays a role in keeping the levels of these miRNAs low under normal conditions (Fig.…”

“…5 We are now presenting, for the first time, data showing the abundance of miRNAs in wing imaginal discs using the more sensitive and unbiased RNA-seq analysis (Fig. S3).…”

“…[1][2][3][4] Furthermore, recent data has shown that ribonucleases can target specific RNAs, which can in turn affect specific cellular pathways. 5,6 However, the effects of ribonucleases on biological functions and the RNAs targeted by specific ribonucleases in whole organisms or tissues are not well understood.…”

Synaptic control of mRNA translation by reversible assembly of XRN1 bodies

“…Invertebrate XRN1 affects embryo development and fly pacman and Caenorhabditis elegans XRN1 control epithelial closure, wound healing and related morphological processes. Lower eukaryote XRN1 influences cell proliferation, and mutations in plant XNR4 affect the stress response and generate developmental abnormalities (Newbury and Woollard, 2004;Jones et al, 2013;Nagarajan et al, 2013). The biological relevance of vertebrate XRN1 is poorly described and, here, we show that rodent XRN1 responds to synaptic activity and regulates protein synthesis in hippocampal neurons.…”

The roles of the exoribonucleases DIS3L2 and XRN1 in human disease

“…In multi-cellular organisms, it is increasingly evident that degradation of specific mRNAs is critical for the regulation of many cellular processes, including early development, infection and inflammation, apoptosis, and ageing [2][3][4][5][6][7]. Although progress has been made in identifying the targets regulated by these ribonucleases [8][9][10][11], the mechanisms whereby they affect cellular processes leading to disease are largely unknown. This review focusses on two highly conserved cytoplasmic exoribonucleases, DIS3L2 and XRN1, and how dysregulation of these enzymes is implicated in human diseases.…”