The rockefeller university

Post-transcriptional gene regulation is robustly regulated by RNA-binding proteins (RBPs). Here we describe the collection of RNAs regulated by AUF1 (AU-binding factor 1), an RBP linked to cancer, inflammation and aging. Photoactivatable ribonucleoside-enhanced crosslinking and immunoprecipitation (PAR-CLIP) analysis reveals that AUF1 primarily recognizes U-/GU-rich sequences in mRNAs and noncoding RNAs and influences target transcript fate in three main directions. First, AUF1 lowers the steady-state levels of numerous target RNAs, including long noncoding RNA NEAT1, in turn affecting the organization of nuclear paraspeckles. Second, AUF1 does not change the abundance of many target RNAs, but ribosome profiling reveals that AUF1 promotes the translation of numerous mRNAs in this group. Third, AUF1 unexpectedly enhances the steady-state levels of several target mRNAs encoding DNA-maintenance proteins. Through its actions on target RNAs, AUF1 preserves genomic integrity, in agreement with the AUF1-elicited prevention of premature cellular senescence.

Background: The high rate of comorbidity between depression and cocaine addiction suggests shared molecular mechanisms and anatomical pathways. Limbic structures, such as the nucleus accumbens (NAc), play a crucial role in both disorders, yet how different cell types within these structures contribute to the pathogenesis remains elusive. Downregulation of p11 (S100A10), specifically in the NAc, elicits depressive-like behaviors in mice, but its role in drug addiction is unknown. Methods: We combined mouse genetics and viral strategies to determine how the titration of p11 levels within the entire NAc affects the rewarding actions of cocaine on behavior (six to eight mice per group) and molecular correlates (three experiments, five to eight mice per group). Finally, the manipulation of p11 expression in distinct NAc dopaminoceptive neuronal subsets distinguished cell-type specific effects of p11 on cocaine reward (five to eight mice per group). Results: We demonstrated that p11 knockout mice have enhanced cocaine conditioned place preference, which is reproduced by the focal downregulation of p11 in the NAc of wild-type mice. In wild-type mice, cocaine reduced p11 expression in the NAc, while p11 overexpression exclusively in the NAc reduced cocaine conditioned place preference. Finally, we identified dopamine receptor-1 expressing medium spiny neurons as key mediators of the effects of p11 on cocaine reward. Conclusions: Our data provide evidence that disruption of p11 homeostasis in the NAc, particularly in dopamine receptor-1 expressing medium spiny neurons, may underlie pathophysiological mechanisms of cocaine rewarding action. Treatments to counter maladaptation of p11 levels may provide novel therapeutic opportunities for cocaine addiction.

Background: The relationship between the pathogenic amyloid beta-peptide species A beta 1-42 and tau pathology has been well studied and suggests that A beta 1-42 can accelerate tau pathology in vitro and in vivo. The manners if any in which A beta 1-40 interacts with tau remains poorly understood. In order to answer this question, we used cell-based system, transgenic fly and transgenic mice as models to study the interaction between A beta 1-42 and A beta 1-40. Results: In our established cellular model, live cell imaging (using confocal microscopy) combined with biochemical data showed that exposure to A beta 1-42 induced cleavage, phosphorylation and aggregation of wild-type//full length tau while exposure to A beta 1-40 didn't. Functional studies with A beta 1-40 were carried out in tau-GFP transgenic flies and showed that A beta 1-42, as previously reported, disrupted cytoskeletal structure while A beta 1-40 had no effect at same dose. To further explore how A beta 1-40 affects tau pathology in vivo, P301S mice (tau transgenic mice) were injected intracerebrally with either A beta 1-42 or A beta 1-40. We found that treatment with A beta 1-42 induced tau phosphorylation, cleavage and aggregation of tau in P301S mice. By contrast, A beta 1-40 injection didn't alter total tau, phospho-tau (recognized by PHF-1) or cleavage of tau, but interestingly, phosphorylation at Ser(262) was shown to be significantly decreased after direct inject of A beta 1-40 into the entorhinal cortex of P301S mice. Conclusions: These results demonstrate that A beta 1-40 plays different role in tau pathogenesis compared to A beta 1-42. A beta 1-40 may have a protective role in tau pathogenesis by reducing phosphorylation at Ser(262), which has been shown to be neurotoxic.

An astounding property of the nervous system is its cellular diversity. This diversity, which was initially realized by morphological and electrophysiological differences, is ultimately produced by variations in gene-expression programs. In most cases, these variations are determined by external cues. However, a growing number of neuronal types have been identified in which inductive signals cannot explain the few but decisive transcriptional differences that cause cell diversification. Here, we show that heterochromatic silencing, which we find is governed by histone methyltransferases G9a (KMT1C) and GLP (KMT1D), is essential for stochastic and singular olfactory receptor (OR) expression. Deletion of G9a and GLP dramatically reduces the complexity of the OR transcriptome, resulting in transcriptional domination by a few ORs and loss of singularity in OR expression. Thus, our data suggest that, in addition to its previously known functions, heterochromatin creates an epigenetic platform that affords stochastic, mutually exclusive gene choices and promotes cellular diversity.

Hepatitis C virus (HCV) particles associate with lipoproteins and infect cells by using at least four cell entry factors. These factors include scavenger receptor class B type I (SR-BI), CD81, claudin 1 (CLDN1), and occludin (OCLN). Little is known about specific functions of individual host factors during HCV cell entry and viral domains that mediate interactions with these factors. Hypervariable region 1 (HVR1) within viral envelope protein 2 (E2) is involved in the usage of SR-BI and conceals the viral CD81 binding site. Moreover, deletion of this domain alters the density of virions. We compared lipoprotein interaction, surface attachment, receptor usage, and cell entry between wild-type HCV and a viral mutant lacking this domain. Deletion of HVR1 did not affect CD81, CLDN1, and OCLN usage. However, unlike wild-type HCV, HVR1-deleted viruses were not neutralized by antibodies and small molecules targeting SR-BI. Nevertheless, modulation of SR-BI cell surface expression altered the infection efficiencies of both viruses to similar levels. Analysis of affinity-purified virions revealed comparable levels of apolipoprotein E (ApoE) incorporation into viruses with or without HVR1. However, ApoE incorporated into these viruses was differentially recognized by ApoE-specific antibodies. Thus, SR-BI has at least two functions during cell entry. One of them can be neutralized by SR-BI-targeting molecules, and it is critical only for wild-type HCV. The other one is important for both viruses but apparently is not inactivated by the SR-BI binding antibodies and small molecules evaluated here. In addition, HVR1 modulates the conformation and/or epitope exposure of virus particle-associated ApoE. IMPORTANCE HCV cell entry is SR-BI dependent irrespective of the presence or absence of HVR1. Moreover, this domain modulates the properties of ApoE on the surface of virus particles. These findings have implications for the development of SR-BI-targeting antivirals. Furthermore, these findings highlight separable functions of SR-BI during HCV cell entry and reveal a novel role of HVR1 for the properties of virus-associated lipoproteins.