Arginyl-tRNA-protein transferase 1 contributes to governing optimal stability of the human immunodeficiency virus type 1 core.

BACKGROUND: The genome of human immunodeficiency virus type 1 (HIV-1) is encapsulated in a core consisting of viral capsid proteins (CA). After viral entry, the HIV-1 core dissociates and releases the viral genome into the target cell, this process is called uncoating. Uncoating of HIV-1 core is one of the critical events in viral replication and several studies show that host proteins positively or negatively regulate this process by interacting directly with the HIV-1 CA. RESULTS: Here, we show that arginyl-tRNA-protein transferase 1 (ATE1) plays an important role in the uncoating process by governing the optimal core stability. Yeast two-hybrid screening of a human cDNA library identified ATE1 as an HIV-1-CA-interacting protein and direct interaction of ATE1 with Pr55gag and p160gag - pol via HIV-1 CA was observed by cell-based pull-down assay. ATE1 knockdown in HIV-1 producer cells resulted in the production of less infectious viruses, which have normal amounts of the early products of the reverse transcription reaction but reduced amounts of the late products of the reverse transcription. Interestingly, ATE1 overexpression in HIV-1 producer cells also resulted in the production of poor infectious viruses. Cell-based fate-of-capsid assay, a commonly used method for evaluating uncoating by measuring core stability, showed that the amounts of pelletable cores in cells infected with the virus produced from ATE1-knockdown cells increased compared with those detected in the cells infected with the control virus. In contrast, the amounts of pelletable cores in cells infected with the virus produced from ATE1-overexpressing cells decreased compared with those detected in the cells infected with the control virus. CONCLUSIONS: These results indicate that ATE1 expression levels in HIV-1 producer cells contribute to the adequate formation of a stable HIV-1 core. These findings provide insights into a novel mechanism of HIV-1 uncoating and revealed ATE1 as a new host factor regulating HIV-1 replication.

Trametinib suppresses HIV-1 replication by interfering with the disassembly of human immunodeficiency virus type 1 capsid core.

Our previous study showed that the phosphorylation of a highly conserved serine residue, Ser16 in the human immunodeficiency virus type 1 (HIV-1) capsid (CA) protein is promoted by virion-incorporated extracellular signal-regulated kinase 2 (ERK2) and required for proper peptidyl-prolyl isomerase (Pin1)-mediated uncoating. Interestingly, western blot analysis demonstrated that phosphorylated/activated mitogen-activated protein kinase kinase 1/2 (MEK1/2), the upstream activator of ERK2, as well as ERK2 are incorporated into virions. Here, we show that the MEK1/2 selective allosteric inhibitor Trametinib reduces HIV-1 infectivity via the decrease in virion-incorporated ERK2 phosphorylation. The treatment of chronic HIV-1-infected T-cell line, CEM/LAV-1 cells with Trametinib results in a decrease in ERK2 phosphorylation in the virions. The viruses have relatively low infectivity and impaired reverse transcription. Cell-based fate-of-capsid uncoating assay showed that the reduction in infectivity was caused by a functional impairment of the uncoating process. Furthermore, the viruses from Trametinib-treated CEM/LAV-1 cells also showed decreased reverse transcription efficiency and attenuated multiple rounds of replication in human peripheral blood mononuclear cells (PBMCs). Taken together, these findings suggest that Trametinib suppresses HIV-1 replication by abrogating the proper disassembly of CA core.

Renal cell carcinoma in patients with acquired cystic disease of the kidney: assessment using a combination of T2-weighted, diffusion-weighted, and chemical-shift MRI without the use of contrast material.

PURPOSE: To evaluate the MRI findings of renal cell carcinoma (RCC), including findings on diffusion-weighted images (DWIs) and chemical shift images (CSIs), in patients with acquired cystic disease of the kidney (ACDK) in relation to the histopathologic findings. MATERIALS AND METHODS: Two radiologists retrospectively reviewed the MRI findings of 10 RCCs in seven consecutive patients with ACDK. They evaluated the signal intensities (SIs) and signal homogeneity of the lesions on T2-weighted images, DWIs, and T1-weighted images. Thereafter, they evaluated the cytoplasmic fat in the lesions by CSIs. After image analyses, the MRI findings were correlated with the histopathologic findings. RESULTS: The RCCs tended to show heterogeneous high SIs on T2-weighted images and DWIs. The high SIs on DWIs were mainly attributable to the viable parts, and the heterogeneity was due to the various SIs arising from the intratumoral degenerative components. Unlike the reported findings for hemorrhagic cysts, the RCCs did not show homogeneous high SIs or fluid-iron levels on T1-weighted images. The four lesions, in which the presence of cytoplasmic fat was suggested on CSIs, were clear cell RCCs. CONCLUSION: The MRI findings, including findings on DWIs and CSIs, well reflected the histopathologic findings of RCC in patients with ACDK.

Preoperative T categorization and prediction of histopathologic grading of urothelial carcinoma in renal pelvis using diffusion-weighted MRI.

OBJECTIVE: The purpose of our study was to evaluate the utility of diffusion-weighted MRI (DWI) for preoperative T categorization and prediction of the histopathologic grade of renal pelvic cancer. MATERIALS AND METHODS: We retrospectively evaluated 40 renal pelvic cancers from 40 patients. The MRI included T2-weighted single-shot fast spin-echo, DWI, and contrast-enhanced imaging. Two radiologists independently reviewed three image sets (T2-weighted images alone, T2-weighted plus DWI, and T2-weighted plus contrast-enhanced images) regarding tumor detection and the discrimination of locally advanced tumors. The diagnostic performance among the three image sets were compared using Cochrane test followed by McNemar tests. The apparent diffusion coefficients between two histopathologic grades were compared using the Mann-Whitney U test. RESULTS: T2-weighted imaging plus DWI enabled a high detection rate (98%, 39/40) without significant differences. For the diagnosis of T3 or higher categories, the accuracies were relatively low in all three image sets (70% each for T2-weighted imaging plus DWI and T2-weighted imaging plus contrast-enhanced imaging and 58% for T2-weighted imaging alone, p > 0.05), with sensitivities of 58%, 65%, and 54%, respectively. For discriminating tumors with macroscopic renal invasion from those with microscopic renal invasion or less, T2-weighted imaging plus DWI (93%) was significantly more accurate than T2-weighted imaging alone (75%) (p = 0.016). The mean apparent diffusion coefficient of the high-grade tumors was significantly lower than that of the low-grade tumors (p < 0.01). CONCLUSION: DWI could be used for preoperative T categorization and prediction of the histopathologic grade of renal pelvic cancer without contrast material.

Comparison of T2-weighted and contrast-enhanced T1-weighted MR imaging at 1.5 T for assessing the local extent of cervical carcinoma.

OBJECTIVE: To compare two MR sequences at 1.5 T-T2-weighted and contrast-enhanced T1-weighted images-by using macroscopic sections to determine which image type enables the most accurate assessment of cervical carcinoma. METHODS: Forty consecutive patients (mean age, 39.2 years) with biopsy-proven cervical carcinoma were included. Each MR sequence was assessed for tumour localisations, tumour margins, and cancer extent with the consensus of two readers, and tumour margins were rated on a five-point scale. MR findings were correlated with histopathological findings. Contrast-to-noise ratios (CNRs) obtained with each image were compared using nonparametric tests. RESULTS: Thirty-one of 40 patients underwent hysterectomies and nine of 40 underwent trachelectomies. In 36 patients, lesions were identified on at least one sequence. The tumours at stage 1B or higher were detected in 94.7% on contrast-enhanced T1-weighted images and in 76.3% on T2-weighted images (P < 0.05). Tumour margins appeared significantly more distinct on contrast-enhanced T1-weighted images than on T2-weighted images (P < 0.001). The CNRs obtained using contrast-enhanced T1-weighted images were significantly higher (P < 0.001) than those obtained using T2-weighted images. CONCLUSION: Contrast-enhanced T1-weighted imaging is more useful for assessing cervical carcinoma than T2-weighted imaging.

The clinical value of bilateral breast MR imaging: is it worth performing on patients showing suspicious microcalcifications on mammography?

The purpose of this study was to evaluate the clinical value of bilateral breast magnetic resonance (MR) imaging (MRI) in patients showing suspicious microcalcifications on mammography and negative ultrasound findings. Fifty patients underwent MRI before stereotactic vacuum-assisted breast biopsy (SVAB). MR findings were classified into five types for interpretation, and types 4 and 5 were considered malignant. SVAB revealed 13 carcinomas and 37 benign lesions. Malignant lesions were more frequently found in cases of positive MRI diagnoses than in negative MRI diagnoses (P < 0.001). Mammography had a sensitivity of 100%, a specificity of 24% and an accuracy of 44%, whereas mammography plus MRI had a sensitivity of 85%, a specificity of 100% and an accuracy of 96%. In the evaluation of mammographically detected microcalcifications, bilateral breast MRI is of good diagnostic value and may alter the indications for SVAB.