No abstract

Background Orientia tsutsugamushi, the causative agent of scrub typhus, is an obligate intracellular bacterium. Previously, a large number of genes that encode proteins containing eukaryotic protein-protein interaction motifs such as ankyrin-repeat (Ank) domains were identified in the O. tsutsugamushi genome. However, little is known about the Ank protein function in O. tsutsugamushi. Methodology/Principal FindingsTo characterize the function of Ank proteins, we investigated a group of Ank proteins containing an F-box–like domain in the C-terminus in addition to the Ank domains. All nine selected ank genes were expressed at the transcriptional level in host cells infected with O. tsutsugamushi, and specific antibody responses against three Ank proteins were detected in the serum from human patients, indicating an active expression of the bacterial Ank proteins post infection. When ectopically expressed in HeLa cells, the Ank proteins of O. tsutsugamushi were consistently found in the nucleus and/or cytoplasm. In GST pull-down assays, multiple Ank proteins specifically interacted with Cullin1 and Skp1, core components of the SCF1 ubiquitin ligase complex, as well as the eukaryotic elongation factor 1 α (EF1α). Moreover, one Ank protein co-localized with the identified host targets and induced downregulation of EF1α potentially via enhanced ubiquitination. The downregulation of EF1α was observed consistently in diverse host cell types infected with O. tsutsugamushi.Conclusion/SignificanceThese results suggest that conserved targeting and subsequent degradation of EF1α by multiple O. tsutsugamushi Ank proteins could be a novel bacterial strategy for replication and/or pathogenesis during mammalian host infection.

The goal of this study was to investigate the relative contributions of different cellular and genetic components to biological samples created by touch or contact with a surface – one of the most challenging forms of forensic evidence. Touch samples were generated by having individuals hold an object for five minutes and analyzed for quantity of intact epidermal cells, extracellular DNA, and DNA from pelleted cell material after elution from the collection swab. Comparisons were made between samples where individuals had washed their hands immediately prior to handling and those where hand washing was not controlled. The vast majority (84-100%) of DNA detected in these touch samples was extracellular and was uncorrelated to the number of epidermal cells detected. Although little to no extracellular or cell pellet-associated DNA was detected when individuals washed their hands prior to substrate handling, we found that a significant number of epidermal cells (between ~5x10 3 and ~1x10 5) could still be recovered from these samples, suggesting that other types of biological information may be present even when no amplifiable nuclear DNA is present. These results help to elucidate the biological context for touch samples and characterize factors that may contribute to patterns of transfer and persistence of genetic material in forensic evidence.

Human cytomegalovirus (HCMV) has many strategies to survive the attack of the host. HCMV infection of host cells induces cellular activation and disturbance of the cell cycle. It is possible that HCMV modulates the behavior of certain cancer cells that are susceptible to HCMV infection. This study was performed to identify the possible mechanism of resistance to apoptotic stimuli in some cancer cell lines by HCMV infection. HCMV‐infected cancer cells showed resistance to apoptosis induced by the topoisomerase II inhibitor etoposide. UMG1–2, which constitutively expresses HCMV immediate‐early protein‐1 (IE1), had resistance to apoptosis induced by etoposide as compared with the parental cell line U373MG. Measurement of caspases activity with fluorogenic substrates in etoposide‐treated U373MG and UMG1–2 cells and the direct activation of caspase‐3 with peptides containing arginine‐glycine‐aspartate in U373MG and UMG1–2 cells revealed that the inhibition level of apoptosis by HCMV IE1 would be upstream of caspase‐3 in the caspase cascade pathway. Cellular expression of Cdk2 was increased in UMG1–2 after etoposide treatment while the expression of E2F‐1 in UMG1–2 was decreased as compared with that in U373MG. The Cdk2 inhibitor, roscovitine, decreased the resistance to apoptosis on etoposide‐treated UMG1–2. These results suggest that aberrant HCMV infection confers resistance to anticancer drugs on some cancer cells and protects cells from apoptosis, possibly due to the deregulation of cyclin‐dependent kinase by HCMV immediate‐early protein.