Dual mode of DDX3X as an ATP-dependent RNA helicase and ATP-independent nucleic acid chaperone.

Human DDX3X, an important member of the DEAD-box family RNA helicases, plays a crucial role in RNA metabolism and is involved in cancer development, viral infection, and neurodegenerative disease. Although there have been many studies on the physiological functions of human DDX3X, issues regarding its exact targets and mechanisms of action remain unclear. In this study, we systematically characterized the biochemical activities and substrate specificity of DDX3X. The results demonstrate that DDX3X is a bidirectional RNA helicase to unwind RNA duplex and RNA-DNA hybrid driven by ATP. DDX3X also has nucleic acid annealing activity, especially for DNA. More importantly, it can function as a typical nucleic acid chaperone which destabilizes highly structured DNA and RNA in an ATP-independent manner and promotes their annealing to form a more stable structure. Further truncation mutations confirmed that the highly disordered N-tail and C-tail are critical for the biochemical activities of DDX3X. They are functionally complementary, with the N-tail being crucial. These results will shed new light on our understanding of the molecular mechanism of DDX3X in RNA metabolism and DNA repair, and have potential significance for the development of antiviral/anticancer drugs targeting DDX3X.

Viral resistance to VRC01-like antibodies with mutations in loop D and V5 from an HIV-1 B' subtype infected individual with broadly neutralization activity.

Recently we identified the VRC01-like antibody DRVIA7(A7) from an HIV-1 B' subtype-infected individual (DRVI01) with broad neutralization activity, and almost all viruses from the individual were resistant to both VRC01 and A7 lineage antibodies. Here, we identified and characterized a panel of HIV-1 variants with resistance to VRC01 and A7 using site-directed mutagenesis and swapping amino acid fragments of gp120. Site-directed mutagenesis revealed that E279D/R282K/N460A/T464N of gp120 from DRVI01 produced VRC01-susceptible variants. Multiple mutations significantly increased the neutralization sensitivity to VRC01. Residues N464 located at the tip of the V5 loop were considered irrelevant to the neutralization of VRC01. For DRVI01-derived viruses, the single N464T change fully produced VRC01-resistant variants; conversely, a single T464N mutation generated VRC01-susceptible variants. Alanine scanning revealed that the N464 residue plays a vital role in binding with VRC01. Neutralizing assays against A7 lineage antibodies showed that DRVI01-derived viruses with multiple mutations could be neutralized by A7 lineage antibodies with different neutralizing breadths. Combining the changes in loops D and V5 produced variants that were totally sensitive variants to A7 lineage antibodies.

[Accuracy of prostatic ultrasonography versus MRI in measuring prostate volume].

OBJECTIVE: To compare the accuracy of different methods of measuring the prostate volume (PV) based on the manifestations of prostatic ultrasonography and MRI. METHODS: Using the drainage method, we measured the volumes of 101 prostatic specimens collected from radical prostatectomy. And with the measures obtained as reference standards, we calculated the PV of the patients with the maximum width (W), height (H) and length (L) of the prostates obtained preoperatively by transabdominal ultrasonography (TAUS), transrectal ultrasonography (TRUS) and MRI using the ellipsoidal formula (PV = W × H × L × 0.52), bullet formula (PV = W × H × L × 0.65) and 3D reconstruction technology. We evaluated the accuracy of the above methods using the Mann-Whitney U test, intraclass correlation coefficient (ICC), and Bland-Altman scatterplot. RESULTS: No statistically significant differences were observed between the specimen and preoperative PVs. The ICCs of the specimen PVs obtained by MRI 3D reconstruction, TRUS bullet formula, MRI ellipsoidal formula and TAUS ellipsoidal formula were 0.978, 0.862, 0.857 and 0.745, respectively. The Bland-Altman scatterplot exhibited that the preoperative PV calculated by MRI 3D reconstruction had the highest consistency with that of the specimen PV, followed by that measured by TRUS bullet formula and that obtained by MRI ellipsoidal formula, while that determined by TAUS ellipsoidal formula had a low consistency. CONCLUSION: The MRI 3D reconstruction technology is the most reliable method for the measurement of PV, followed by TRUS bullet formula, but the latter is recommended for its high applicability in clinical practice.

[Experimental study on osteogenesis of acellular porcine pericardium in guided bone regeneration].

PURPOSE: To observe the retention time and effect of acellular porcine pericardium (APP) in bone regeneration for rabbit femoral bone defects. METHODS: APP was prepared as follows: fresh porcine pericardium was chosen, high and low osmotic NaCl solution were used to soak the specimen alternately, trypsin+EDTA were used for digest, and then immersed with TritonX-100, cross-linked by using glutaraldehyde. 24 New Zealand rabbits were selected, and the area of bone defect was created 8 mm×8 mm×5 mm in size on bilateral distal femur. Stochastic method was used for grouping. One side of bone defect was covered with APP (experimental group); and the other side was covered without APP (control group). General observation, X-ray examination, histological examination, and bone mineral density (BMD) were performed 4 weeks, 8 weeks and 12 weeks after operation. SPSS18.0 software package was used for statistical analysis. RESULTS: After surgery, all wounds healed without complications. Under general observation, there were some fibrous cysts covered on the surface of APP. BMD (P<0.05) in the experimental group was significantly greater than that in the control group. On histological examination, the rate of osteogenesis in the experimental group was faster than that in the control group. CONCLUSIONS: Bone regeneration can be achieved using APP in the repair of rabbit bone defects. The retention time of APP can meet the needs of osteogenesis.