A pathway linking translation stress to checkpoint kinase 2 signaling in Neurospora crassa

Abstract

Checkpoint kinase 2 (CHK-2) is a key component of the DNA damage response (DDR). CHK-2 is activated by the PIP3-kinase-like kinases (PI3KKs) ataxia telangiectasia mutated (ATM) and ataxia telangiectasia and Rad3-related protein (ATR), and in metazoan also by DNA-dependent protein kinase catalytic subunit (DNA-PKcs). These DNA damage-dependent activation pathways are conserved and additional activation pathways of CHK-2 are not known. Here we show that PERIOD-4 (PRD-4), the CHK-2 ortholog of Neurospora crassa, is part of a signaling pathway that is activated when protein translation is compromised. Translation stress induces phosphorylation of PRD-4 by a PI3KK distinct from ATM and ATR. Our data indicate that the activating PI3KK is mechanistic target of rapamycin (mTOR). We provide evidence that translation stress is sensed by unbalancing the expression levels of an unstable protein phosphatase that antagonizes phosphorylation of PRD-4 by mTOR complex 1 (TORC1). Hence, Neurospora mTOR and PRD-4 appear to coordinate metabolic state and cell cycle progression.

Multiple random phosphorylations in clock proteins provide long delays and switches

“…About 100 phosphorylation sites have been identified using isotope labelling and mass spectrometry. The priming-independent phosphorylation of non-consensus sites on FRQ by CK1a seems to be slower than five sites per hour 62 . Priming by other kinases is relatively fast and appears to be less essential for the principle function of the core clock.…”

“…We do not explicitly consider phosphatases throughout. Phosphatases are found to be permanently available in cells and it is basically the ratio of kinase and phosphatase which takes the reaction forward 61,62 . It is known that phosphatases are tightly As an example, the FRQ protein is stabilized by FRH and undergoes multiple phosphorylations by CK1a.…”

Multiple random phosphorylations in clock proteins provide long delays and switches

“…About 100 phosphorylation sites have been identified using isotope labelling and mass spectrometry. The priming-independent phosphorylation of non-consensus sites on FRQ by CK1a seems to be slower than 5 sites per hour [54]. Priming by other kinases is relatively fast and appears to be less essential for the principle function of the core clock.…”

“…We do not explicitly consider phosphatases throughout. Phosphatases are found to be permanently available in cells and it is basically the ratio of kinase and phosphatase which takes the reaction forward [53,54]. the increasing levels of different phosphorylations in the linear model.…”

Genome-wide CRISPR synthetic lethality screen identifies a role for the ADP-ribosyltransferase PARP14 in DNA replication dynamics controlled by ATR

“…In addition, this may also reflect a possible activity of PARP14 in directly binding RNA, as PARP14 contains two RRM domains, which are known to bind RNA ( 16 ). On the other hand, protein translation stress has been shown to induce DNA damage and replication stress, and activate the DNA damage response ( 52–54 ). Thus, it is possible that the prevalence of RNA metabolism in the list of top biological pathways showing synthetic lethality with PARP14, indicates a functional connection with the ATR pathway.…”