Effect of DNA Repair Protein Rad18 on Viral Infection

Host factors belonging to the DNA repair machineries are assumed to aid retroviruses in the obligatory step of integration. Here we describe the effect of DNA repair molecule Rad18, a component of the post-replication repair pathway, on viral infection. Contrary to our expectations, cells lacking Rad18 were consistently more permissive to viral transduction as compared to Rad18(+/+) controls. Remarkably, such susceptibility was integration independent, since retroviruses devoid of integration activity also showed enhancement of the initial steps of infection. Moreover, the elevated sensitivity of the Rad18(−/−) cells was also observed with adenovirus. These data indicate that Rad18 suppresses viral infection in a non-specific fashion, probably by targeting incoming DNA. Furthermore, considering data published recently, it appears that the interactions between DNA repair components with incoming viruses, often result in inhibition of the infection rather than cooperation toward its establishment

HIVToolbox, an Integrated Web Application for Investigating HIV

Many bioinformatic databases and applications focus on a limited domain of knowledge federating links to information in other databases. This segregated data structure likely limits our ability to investigate and understand complex biological systems. To facilitate research, therefore, we have built HIVToolbox, which integrates much of the knowledge about HIV proteins and allows virologists and structural biologists to access sequence, structure, and functional relationships in an intuitive web application. HIV-1 integrase protein was used as a case study to show the utility of this application. We show how data integration facilitates identification of new questions and hypotheses much more rapid and convenient than current approaches using isolated repositories. Several new hypotheses for integrase were created as an example, and we experimentally confirmed a predicted CK2 phosphorylation site. Weblink: [http://hivtoolbox.bio-toolkit.com

Sequential Deletion of the Integrase (Gag-Pol) Carboxyl Terminus Reveals Distinct Phenotypic Classes of Defective HIV-1 ▿ † §

A requisite step in the life cycle of human immunodeficiency virus type 1 (HIV-1) is the insertion of the viral genome into that of the host cell, a process catalyzed by the 288-amino-acid (32-kDa) viral integrase (IN). IN recognizes and cleaves the ends of reverse-transcribed viral DNA and directs its insertion into the chromosomal DNA of the target cell. IN function, however, is not limited to integration, as the protein is required for other aspects of viral replication, including assembly, virion maturation, and reverse transcription. Previous studies demonstrated that IN is comprised of three domains: the N-terminal domain (NTD), catalytic core domain (CCD), and C-terminal domain (CTD). Whereas the CCD is mainly responsible for providing the structural framework for catalysis, the roles of the other two domains remain enigmatic. This study aimed to elucidate the primary and subsidiary roles that the CTD has in protein function. To this end, we generated and tested a nested set of IN C-terminal deletion mutants in measurable assays of virologic function. We discovered that removal of up to 15 residues (IN 273) resulted in incremental diminution of enzymatic function and infectivity and that removal of the next three residues resulted in a loss of infectivity. However, replication competency was surprisingly reestablished with one further truncation, corresponding to IN 269 and coinciding with partial restoration of integration activity, but it was lost permanently for all truncations extending N terminal to this position. Our analyses of these replication-competent and -incompetent truncation mutants suggest potential roles for the IN CTD in precursor protein processing, reverse transcription, integration, and IN multimerization