Citations

Chromosomal integration enables human immunodeficiency virus (HIV) to establish a permanent reservoir that can be therapeutically suppressed but not eradicated. Participation of cellular proteins in this obligate replication step is poorly understood. We used intensified RNA interference and dominant-negative protein approaches to show that the cellular transcriptional coactivator lens epithelium–derived growth factor (LEDGF)/p75 (p75) is an essential HIV integration cofactor. The mechanism requires both linkages of a molecular tether that p75 forms between integrase and chromatin. Fractionally minute levels of endogenous p75 are sufficient to enable integration, showing that cellular factors that engage HIV after entry may elude identification in less intensive knockdowns. Perturbing the p75-integrase interaction may have therapeutic potential.

Abstract Motivation: Using stable isotopes in global proteome scans, labeled molecules from one sample are pooled with unlabeled molecules from another sample and subsequently subjected to mass-spectral analysis. Stable-isotope methodologies make use of the fact that identical molecules of different stable-isotope compositions are differentiated in a mass spectrometer and are represented in a mass spectrum as distinct isotopic clusters with a known mass shift. We describe two multivariable linear regression models for 16O/18O stable-isotope labeled data that jointly model pairs of resolved isotopic clusters from the same peptide and quantify the abundance present in each of the two biological samples while concurrently accounting for peptide-specific incorporation rates of the heavy isotope. The abundance measure for each peptide from the two biological samples is then used in down-stream statistical analyses, e.g. differential expression analysis. Because the multivariable regression models are able to correct for the abundance of the labeled peptide that appear as an unlabeled peptide due to the inability to exchange the natural C-terminal oxygen for the heavy isotope, they are particularly advantageous for a two-step digestion/labeling procedure. We discuss how estimates from the regression model are used to quantify the variability of the estimated abundance measures for the paired samples. Although discussed in the context of 16O/18O stable-isotope labeled data, the multivariable regression models are generalizable to other stable-isotope labeled technologies. Contact: eckel@mayo.edu

Inorganic phosphate (Pi) is required for energy metabolism, nucleic acid synthesis, bone mineralization, and cell signaling. The activity of cell-surface sodium-phosphate (Na+-Pi) cotransporters mediates the uptake of Pi from the extracellular environment. Na+-Pi cotransporters and organ-specific Pi absorptive processes are regulated by peptide and sterol hormones, such as parathyroid hormone (PTH) and 1α,25-dihydroxyvitamin D (1α,25(OH)2D3), which interact in a coordinated fashion to regulate Pi homeostasis. Recently, several phosphaturic peptides such as fibroblast growth factor-23 (FGF-23), secreted frizzled related protein-4 (sFRP-4), matrix extracellular phosphoglycoprotein, and fibroblast growth factor-7 have been demonstrated to play a pathogenic role in several hypophosphatemic disorders. By inhibiting Na+-Pi transporters in renal epithelial cells, these proteins increase renal Pi excretion, resulting in hypophosphatemia. FGF-23 and sFRP-4 inhibit 25-hydroxyvitamin D 1α-hydroxylase activity, reducing 1α,25(OH)2D3 synthesis and thus intestinal Pi absorption. This review examines the role of these factors in Pi homeostasis in health and disease.

ABSTRACT Influenza A virus was detected at higher rates and for more extended time periods with real-time PCR than with cell cultures. We show here that, using the theranostic approach, rapid viral detection and reporting can provide for early implementation and assessment of available antiviral therapy.