LEDGF/p75-Independent HIV-1 Replication Demonstrates a Role for HRP-2 and Remains Sensitive to Inhibition by LEDGINs

Lens epithelium–derived growth factor (LEDGF/p75) is a cellular cofactor of HIV-1 integrase (IN) that interacts with IN through its IN binding domain (IBD) and tethers the viral pre-integration complex to the host cell chromatin. Here we report the generation of a human somatic LEDGF/p75 knockout cell line that allows the study of spreading HIV-1 infection in the absence of LEDGF/p75. By homologous recombination the exons encoding the LEDGF/p75 IBD (exons 11 to 14) were knocked out. In the absence of LEDGF/p75 replication of laboratory HIV-1 strains was severely delayed while clinical HIV-1 isolates were replication-defective. The residual replication was predominantly mediated by the Hepatoma-derived growth factor related protein 2 (HRP-2), the only cellular protein besides LEDGF/p75 that contains an IBD. Importantly, the recently described IN-LEDGF/p75 inhibitors (LEDGINs) remained active even in the absence of LEDGF/p75 by blocking the interaction with the IBD of HRP-2. These results further support the potential of LEDGINs as allosteric integrase inhibitors.     

IAPs: guardians of RIPK1

Deregulation of innate immune signalling and cell death form the basis of most human disease pathogenesis. Inhibitor of APoptosis (IAP) protein-family members are frequently overexpressed in cancer and contribute to tumour cell survival, chemo-resistance, disease progression and poor prognosis. Although best known for their ability to regulate caspases, IAPs also influence ubiquitin-dependent pathways that modulate innate immune signalling by activation of NF-κB. Recent advances in our understanding of the molecular mechanisms through which IAPs influence cell death and innate immune responses have provided new insights into novel strategies for treatment of cancer. In this review we discuss our current understanding of IAP-mediated NF-κB signalling, as well as elaborate on unexpected insights into the involvement of IAPs in regulating the 'Ripoptosome', a novel intrinsic cell death-inducing platform. We propose an evolutionarily conserved concept whereby IAPs function as guardians of killer platforms such as the apoptosome in Drosophila and the Ripoptosome in mammals.     

Development of an AlphaScreen-based HIV-1 integrase dimerization assay for discovery of novel allosteric inhibitors

In recent years, HIV-1 integrase (IN) has become an established target in the field of antiretroviral drug discovery. However, its sole clinically approved inhibitor, the integrase strand transfer inhibitor (INSTI) raltegravir, has a surprisingly low genetic barrier for resistance. Furthermore, the only two other integrase inhibitors currently in advanced clinical trials, elvitegravir and dolutegravir, share its mechanism of action and certain resistance pathways. To maintain a range of treatment options, drug discovery efforts are now turning toward allosteric IN inhibitors, which should be devoid of cross-resistance with INSTIs. As IN requires a precise and dynamic equilibrium between several oligomeric species for its activities, the modulation of this equilibrium presents an interesting allosteric target. We report on the development, characterization, and validation of an AlphaScreen-based assay for high-throughput screening for modulators of HIV-1 IN dimerization. Compounds identified as hits in this assay proved to act as allosteric IN inhibitors. Additionally, the assay offers a flexible platform to study IN dimerization.     

On the inappropriate use of Kimura‐2‐parameter (K2P) divergences in the DNA‐barcoding literature

Here we present evidence, based on 10 datasets comprising 5283 sequences for 200 genera, that the use of the Kimura‐2‐parameter (K2P) model in DNA‐barcoding studies is poorly justified. We demonstrate that K2P is neither expected nor confirmed to be an appropriate model for closely related COI sequences. In addition, we show that the use of uncorrected distances yields higher or similar identification success rates for neighbour‐joining trees and distance‐based identification techniques. K2P also does not widen the barcoding gap for closely related sequences. We conclude that the spread of K2P through the barcoding literature is difficult to explain, and urge the use of evidence‐based approaches to DNA barcoding. © The Willi Hennig Society 2011.     

Distribution and habitat features of southern pudu (Pudu puda Molina, 1782) in Argentina

Pudu puda is a very small deer that inhabits humid areas of the temperate forests in Chile and Argentina and is one of the less known South American deer. We provide an updated distribution of Pudu puda in Argentina, with georeferenced sighting localities, and some qualitative features of its habitat such as forest type and understory. We also analyse the effects of human settlements, cattle and invasive mammals (Cervus elaphus and Sus scrofa) on the distribution of the southern pudu. We obtained information on Pudu puda occurrence from unpublished sources including protected areas provided by National Parks Administration and interviews of local residents. In the north sector of Nahuel Huapi National Park, where high density of records was found, we obtained information about some qualitative habitat features, proximity of Pudu puda sighting localities to human settlements, presence of invasive mammals and cattle. We recorded a total of 54 new localities for Pudu puda in Argentina, the northernmost record at S 39°23′, W 71°17′ and the southernmost at S 42°58′, W 72°00′. We recorded low frequency of human settlements, Sus scrofa and Cervus elaphus in Pudu puda sighting localities. We did not detect exclusion of Pudu puda from areas with cattle occurrence. Sighting localities of southern pudu were made mostly in monotypic mature Nothofagus dombeyi forest, with dense understory dominated by Chusquea coleu.     

Daily rhythm of plasma corticosterone binding activity in the white-throated sparrow,Zonotrichiaalbicollis

There is a bimodal daily rhythm of plasma corticosterone binding activity (CBA) in the white-throated sparrow, $\text{Zonotrichia}$$\text{albicollis}$, in the spring migratory condition. Low levels occurred at the beginning (0500) and at the end (2100) of a 16-hour daily photoperiod. Peak CBA occurred at 0900 and 0100, as did peak locomotor activity in this nocturnal migrant. Comparisons of CBA with total plasma corticosteroid concentrations from a previous study of the same group of birds indicate a positive correlation during most of the day but not during the early hours of darkness. The daily rhythm of locomotor activity may account for the rhythm of CBA which, in turn, may be partially responsible for the daily rhythm of plasma corticosteroid concentration.