MAP kinase Slt2p attenuates cell wall mRNA decay by downregulating the RNA-binding protein Rbp1p in response to stress

The yeast cell wall integrity (CWI) MAPK pathway is a signaling cascade function in maintaining cell wall integrity under stressful environmental conditions. Recently, the activity and signaling of Slt2p (Mpk1p) MAP kinase has been shown to control assembly of the processing body (P-body) upon cell wall stresses, implicating its posttranscriptional role in decay of cell wall mRNAs. However, how Slt2p MAP kinase directly regulates the stability of cell wall transcripts during cell wall stress remains unclear. Here, we reported that the RNA-binding protein Rbp1p (Ngr1p) is a downstream effector and target of Slt2p MAP kinase during activation of the cell wall stress signaling cascade. In addition to the well-defined target mitochondrial porin mRNA, we found that Rbp1p also negatively regulates the stability of a subset of Slt2p-regulated cell wall transcripts. Deletion of RBP1 increases the level of cell wall transcripts and partially suppresses the hypersensitivity of the slt2{Delta} deletion strain to cell wall damage. Slt2p is necessary for cell wall stress-induced stabilization of cell wall transcripts. Deletion of RBP1 compromises the destabilization of cell wall transcripts in slt2{Delta} mutants under cell wall stress. Notably, C-terminal deleted Slt2p impairs its function in promoting turnover of the Rbp1p protein and fails to stabilize cell wall transcripts, although it can complement the growth defect of the slt2{Delta} strain upon cell wall stress. Altogether, our results demonstrate that MAP kinase Slt2p attenuates CWI mRNA decay in response to cell wall damage by downregulating the activity of the RNA-binding protein Rbp1p.