The human immunodeficiency virus type 1 (HIV-1) genomic RNA (vRNA) has two major fates during viral replication: to serve as the template for the major structural and enzymatic proteins, or to be encapsidated and packaged into assembling virions to serve as the genomic vRNA in budding viruses. The dynamic balance between vRNA translation and encapsidation is mediated by numerous host proteins, including Staufen1. During HIV-1 infection, HIV-1 recruits Staufen1 to assemble a distinct ribonucleoprotein complex promoting vRNA encapsidation and viral assembly. Staufen1 also rescues vRNA translation and gene expression during conditions of cellular stress. In this work, we utilized novel Staufen1 −/− gene-edited cells to further characterize the contribution of Staufen1 in HIV-1 replication. We observed a marked deficiency in the ability of HIV-1 to dissociate stress granules (SGs) in Staufen1-deficient cells and remarkably, the vRNA repositioned to SGs. These phenotypes were rescued by Staufen1 expression in trans or in cis, but not by a dsRBD-binding mutant, Staufen1F135A. The mistrafficking of the vRNA in these Staufen1 −/− cells was also accompanied by a dramatic decrease in viral production and infectivity. This work provides novel insight into the mechanisms by which HIV-1 uses Staufen1 to ensure optimal vRNA translation and trafficking, supporting an integral role for Staufen1 in the HIV-1 life cycle, positioning it as an attractive target for next-generation antiretroviral agents.

Staufen1 (STAU1) is an RNA-binding protein involved in the post-transcriptional regulation of mRNAs. We report that a large fraction of STAU1 localizes to the mitotic spindle in colorectal cancer HCT116 cells and in non-transformed hTERT-RPE1 cells. Spindle-associated STAU1 partly co-localizes with ribosomes and active sites of translation. We mapped the molecular determinant required for STAU1–spindle association within the first 88 N-terminal amino acids, a domain that is not required for RNA binding. Interestingly, transcriptomic analysis of purified mitotic spindles revealed that 1054 mRNAs and the precursor ribosomal RNA (pre-rRNA), as well as the long non-coding RNAs and small nucleolar RNAs involved in ribonucleoprotein assembly and processing, are enriched on spindles compared with cell extracts. STAU1 knockout causes displacement of the pre-rRNA and of 154 mRNAs coding for proteins involved in actin cytoskeleton organization and cell growth, highlighting a role for STAU1 in mRNA trafficking to spindle. These data demonstrate that STAU1 controls the localization of subpopulations of RNAs during mitosis and suggests a novel role of STAU1 in pre-rRNA maintenance during mitosis, ribogenesis and/or nucleoli reassembly.

Unlike artificial nanosystems, biological systems are ideally engineered to respond to their environment. As such, natural molecular buffers ensure precise and quantitative delivery of specific molecules through self-regulated mechanisms based on Le Chatelier’s principle. Here, we apply this principle to design self-regulated nucleic acid molecular buffers for the chemotherapeutic drug doxorubicin and the antimalarial agent quinine. We show that these aptamer-based buffers can be programmed to maintain any specific desired concentration of free drug both in vitro and in vivo and enable the optimization of the chemical stability, partition coefficient, pharmacokinetics and biodistribution of the drug. These programmable buffers can be built from any polymer and should improve patient therapeutic outcome by enhancing drug activity and minimizing adverse effects and dosage frequency.

STATEMENT 1 Proper localization and functions of macromolecules during cell division are crucial to 2 ensure survival and proliferation of daughter cells. 3 4 ABSTRACT 1 Staufen1 (STAU1) is an RNA-binding protein involved in the posttranscriptional 2 regulation of mRNAs. We report that a large fraction of STAU1 localizes to the mitotic 3 spindle in the colorectal cancer HCT116 and in the non-transformed hTERT-RPE1 cells. 4Spindle-associated STAU1 partly co-localizes with ribosomes and active sites of 5 translation. We mapped the molecular determinant required for STAU1/spindle association 6 within the first 88 N-terminal amino acids, a domain that is not required for RNA binding. 7Interestingly, transcriptomic analysis of purified mitotic spindles reveals that 1054 mRNAs 8 as well as the precursor ribosomal RNA and lncRNAs and snoRNAs involved in 9 ribonucleoprotein assembly and processing are enriched on spindles compared to cell 10 extracts. STAU1 knockout causes the displacement of the pre-rRNA and of 154 mRNAs 11 coding for proteins involved in actin cytoskeleton organization and cell growth, 12 highlighting a role for STAU1 in mRNA trafficking to spindle. These data demonstrate 13 that STAU1 controls the localization of sub-populations of RNAs during mitosis and 14 suggests a novel role of STAU1 in pre-rRNA maintenance during mitosis, ribogenesis 15 and/or nucleoli reassembly. 16 17 18

No abstract