Coordinate regulation of the senescent state by selective autophagy.
PABP Cooperates with the CCR4-NOT Complex to Promote mRNA Deadenylation and Block Precocious Decay
2018; 70 (6): 1081-+
Cellular senescence is a complex stress response implicated in aging. Autophagy can suppress senescence but is counterintuitively necessary for full senescence. Although its anti-senescence role is well described, to what extent autophagy contributes to senescence establishment and the underlying mechanisms is poorly understood. Here, we show that selective autophagy of multiple regulatory components coordinates the homeostatic state of senescence. We combined a proteomic analysis of autophagy components with protein stability profiling, identifying autophagy substrate proteins involved in several senescence-related processes. Selective autophagy of KEAP1 promoted redox homeostasis during senescence. Furthermore, selective autophagy limited translational machinery components to ameliorate senescence-associated proteotoxic stress. Lastly, selective autophagy of TNIP1 enhanced senescence-associated inflammation. These selective autophagy networks appear to operate invivo senescence during human osteoarthritis. Our data highlight a caretaker role of autophagy in the stress support network of senescence through regulated protein stability and unravel the intertwined relationship between two important age-related processes.
View details for DOI 10.1016/j.devcel.2021.04.008
View details for PubMedID 33915088
Regulation of Poly(A) Tail and Translation during the Somatic Cell Cycle
2016; 62 (3): 462?71
Multiple deadenylases are known in vertebrates, the PAN2-PAN3 (PAN2/3) and CCR4-NOT (CNOT) complexes, and PARN, yet their differential functions remain ambiguous. Moreover, the role of poly(A) binding protein (PABP) is obscure, limiting our understanding of the deadenylation mechanism. Here, we show that CNOT serves as a predominant nonspecific deadenylase for cytoplasmic poly(A)+ RNAs, and PABP promotes deadenylation while preventing premature uridylation and decay. PAN2/3 selectively trims long tails (>?150 nt) with minimal effect on transcriptome, whereas PARN does not affect mRNA deadenylation. CAF1 and CCR4, catalytic subunits of CNOT, display distinct activities: CAF1 trims naked poly(A) segments and is blocked by PABPC, whereas CCR4 is activated by PABPC to shorten PABPC-protected sequences. Concerted actions of CAF1 and CCR4 delineate the ?27 nt periodic PABPC footprints along shortening tail. Our study unveils distinct functions of deadenylases and PABPC, re-drawing the view on mRNA deadenylation and regulation.
View details for DOI 10.1016/j.molcel.2018.05.009
View details for Web of Science ID 000436640300012
View details for PubMedID 29932901
PKR is activated by cellular dsRNAs during mitosis and acts as a mitotic regulator
GENES & DEVELOPMENT
2014; 28 (12): 1310?22
Poly(A) tails are critical for mRNA stability and translation. However, recent studies have challenged this view, showing that poly(A) tail length and translation efficiency are decoupled in non-embryonic cells. Using TAIL-seq and ribosome profiling, we investigate poly(A) tail dynamics and translational control in the somatic cell cycle. We find dramatic changes in poly(A) tail lengths of cell-cycle regulatory genes like CDK1, TOP2A, and FBXO5, explaining their translational repression in M phase. We also find that poly(A) tail length is coupled to translation when the poly(A) tail is <20 nucleotides. However, as most genes have >20 nucleotide poly(A) tails, their translation is regulated mainly via poly(A) tail length-independent mechanisms during the cell cycle. Specifically, we find that terminal oligopyrimidine (TOP) tract-containing transcripts escape global translational suppression in M phase and are actively translated. Our quantitative and comprehensive data provide a revised view of translational control in the somatic cell cycle.
View details for DOI 10.1016/j.molcel.2016.04.007
View details for Web of Science ID 000376444700015
View details for PubMedID 27153541
The RNA-binding protein repertoire of embryonic stem cells
NATURE STRUCTURAL & MOLECULAR BIOLOGY
2013; 20 (9): 1122-+
dsRNA-dependent protein kinase R (PKR) is a ubiquitously expressed enzyme well known for its roles in immune response. Upon binding to viral dsRNA, PKR undergoes autophosphorylation, and the phosphorylated PKR (pPKR) regulates translation and multiple signaling pathways in infected cells. Here, we found that PKR is activated in uninfected cells, specifically during mitosis, by binding to dsRNAs formed by inverted Alu repeats (IRAlus). While PKR and IRAlu-containing RNAs are segregated in the cytosol and nucleus of interphase cells, respectively, they interact during mitosis when nuclear structure is disrupted. Once phosphorylated, PKR suppresses global translation by phosphorylating the ? subunit of eukaryotic initiation factor 2 (eIF2?). In addition, pPKR acts as an upstream kinase for c-Jun N-terminal kinase and regulates the levels of multiple mitotic factors such as cyclins A and B and Polo-like kinase 1 and phosphorylation of histone H3. Disruption of PKR activation via RNAi or expression of a transdominant-negative mutant leads to misregulation of the mitotic factors, delay in mitotic progression, and defects in cytokinesis. Our study unveils a novel function of PKR and endogenous dsRNAs as signaling molecules during the mitosis of uninfected cells.
View details for DOI 10.1101/gad.242644.114
View details for Web of Science ID 000337991000005
View details for PubMedID 24939934
View details for PubMedCentralID PMC4066401
RNA-binding proteins (RBPs) have essential roles in RNA-mediated gene regulation, and yet annotation of RBPs is limited mainly to those with known RNA-binding domains. To systematically identify the RBPs of embryonic stem cells (ESCs), we here employ interactome capture, which combines UV cross-linking of RBP to RNA in living cells, oligo(dT) capture and MS. From mouse ESCs (mESCs), we have defined 555 proteins constituting the mESC mRNA interactome, including 283 proteins not previously annotated as RBPs. Of these, 68 new RBP candidates are highly expressed in ESCs compared to differentiated cells, implicating a role in stem-cell physiology. Two well-known E3 ubiquitin ligases, Trim25 (also called Efp) and Trim71 (also called Lin41), are validated as RBPs, revealing a potential link between RNA biology and protein-modification pathways. Our study confirms and expands the atlas of RBPs, providing a useful resource for the study of the RNA-RBP network in stem cells.
View details for DOI 10.1038/nsmb.2638
View details for Web of Science ID 000324160900017
View details for PubMedID 23912277