Daher, C. | bioRxiv Science

bioRxiv2019

Nuclear poly(A) tail size is regulated by Cnot1 during the serum response

The poly(A) tail removal from mRNAs introduces a delay between mRNA synthesis and decay. We measured levels and poly(A) tail sizes of serum-induced mRNAs and used mathematical modelling to compare their deadenylation time with the delay in decay and found that they are indeed correlated. Discrepancies between our data and the polyadenylation models at later time points after the peak of induction led us to investigate the size of the poly(A) tails on newly made mRNA. Surprisingly, new serum-induced mRNAs synthesised late in induction had short poly(A) tails (around A25) in the nucleus. In addition, newly made constitutive mRNAs had medium sized poly(A) tails (around A50). To see if deadenylation was responsible for the new short poly(A) tails, we depleted Cnot1, a subunit of the CCR4/NOT deadenylase. Cnot1 depletion led to slower deadenylation of cytoplasmic mRNAs, as expected, but also decreased transcription and led to longer nuclear mRNA poly(A) tails. These observations implicate CCR4/NOT in regulating both the transcription and the nuclear poly(A) tail size of serum-induced mRNAs. Detection of some chromatin-associated mRNAs with long poly(A) tails suggested that nuclear deadenylation is an early event. Our data show that initial poly(A) tail size of mRNAs can be regulated and is not always 200-250 nucleotides, adding a novel layer to the control of gene expression.

molecular biology↗

bioRxiv2018

Blockade of β-adrenergic receptor signaling improves cancer vaccine efficacy through its effect on naive CD8+ T-cell priming

{beta}-adrenergic receptor ({beta}-AR) signaling, by acting directly on tumor cells and angiogenesis, has been showed to exert pro-tumoral effects. Growing evidence also suggests that {beta}-AR expressed by immune cells affect the associated anti-tumor immune response. However, how and where {beta}-AR signaling impinges the anti-tumor immune response is still unclear. Using a mouse model of vaccine-based immunotherapy, we show here that propranolol, a non-selective {beta}-blocker, strongly improved the efficacy of the vaccine by enhancing the frequency of CD8+ T lymphocytes infiltrating the tumor (TILs). However, propranolol had no obvious effect on the reactivity of CD8+ TILs, a result further strengthened by ex-vivo experiments showing that these cells are insensitive to AR signaling triggered by adrenaline or noradrenaline. In contrast, we show that naive CD8+ T cell activation was strongly inhibited by {beta}-AR signaling and that the beneficial effect of propranolol mainly occurred during their initial priming phase. We also demonstrate that the differential sensitivity of CD8+ TILs and naive CD8+ T cells is related to their activation status since in vitro-activated CD8+ T cells behaved similarly to CD8+ TILs, both exhibiting a down-regulation of the {beta}2-AR expression. These results reveal that the initial priming phase of the anti-tumor response in the tumor-draining lymph node is a decisive part of the suppressive effect of {beta}-AR signaling on the CD8+ T-cell response against cancer. These findings provide a rationale for the strategic use of clinically available {beta}-blockers in patients to improve cancer immunotherapies such as anti-cancer vaccination strategies.

immunology↗