A novel Smg6 mouse model reveals regulation of circadian period and daily CRY2 accumulation through the nonsense-mediated mRNA decay pathway

Abstract

Nonsense-mediated mRNA decay (NMD) has been intensively studied as a surveillance pathway that degrades erroneous transcripts arising from mutations or RNA processing errors. While additional roles in controlling regular mRNA stability have emerged, possible functions in mammalian physiology in vivo have remained unclear. Here, we report a novel conditional mouse allele that allows converting the NMD effector nuclease SMG6 from wild-type to nuclease domain-mutant protein. We analyzed how NMD downregulation affects the function of the circadian clock, a system known to require rapid mRNA turnover. We uncover strong lengthening of free-running circadian periods for liver and fibroblast clocks, and direct NMD regulation of Cry2 mRNA, encoding a key transcriptional repressor within the rhythm-generating feedback loop. In the entrained livers of Smg6 mutant animals we reveal transcriptome-wide alterations in daily mRNA accumulation patterns, altogether expanding the known scope of NMD regulation in mammalian gene expression and physiology.

Transcriptome-wide analysis of primary human endothelial cell responses to 1 hour of protein translation inhibition identify nonsense mediated decay targets and a non-codingSLC11A2exon as an acute biomarker

“…[1,2] NMD plays regulatory roles throughout the eukaryotic kingdom, is translation dependent, and reversed by broad protein synthesis inhibitors such as cycloheximide, [3] in addition to more NMD specific regulators. [4][5][6][7] NMD is blunted by a number of stressors including endoplasmic reticulum stress when unfolded or misfolded proteins are accumulating, and exogenous stress when NMD is downregulated as a consequence of stress signals that inhibit protein translation. [8][9][10] In turn, the integrated stress response which is triggered by multiple stresses such as reactive oxygen species (ROS) generation, hypoxia, and limited amino acid supply, depends upon key natural NMD targets (ATF3, ATF4 and CHOP) that provide mechanisms to augment cellular stress responses.…”

“…[1,2] NMD depends upon the highly conserved ATP-dependent RNA helicase UPF1, [4,7] with activity moderated by varying NMD factors in different settings. [1,2,[4][5][6][7][8] NMD is illustrated in a simplified manner in Figure 1A.…”

“…[13] Up to 50% of human transcripts contain at least one upstream open reading frame (uORF) which contains a PTC that can trigger NMD when the uORF is used. [14] New data highlight a role for NMD in circadian clock regulation of gene expression, [6] and further examples are described in recent data manuscripts and reviews. [1,2,[4][5][6][7] Thus, the cellular environment differs according to the degree to which NMD is operational, and biomarkers of such a state would be valuable for experimental cell biologists.…”