Purified retrovirus Gag proteins or Gag protein fragments are able to assemble into virus-like particles (VLPs) in vitro in the presence of RNA. We have examined the role of nucleic acid and of the NC domain in assembly of VLPs from a Rous sarcoma virus (RSV) Gag protein and have characterized these VLPs using transmission electron microscopy (TEM), scanning TEM (STEM), and cryoelectron microscopy (cryo-EM). RNAs of diverse sizes, single-stranded DNA oligonucleotides as small as 22 nucleotides, double-stranded DNA, and heparin all promoted efficient assembly. The percentages of nucleic acid by mass, in the VLPs varied from 5 to 8%. The mean mass of VLPs, as determined by STEM, was 6.5 ؋ 10 7 Da for both RNA-containing and DNA oligonucleotide-containing particles, corresponding to a stoichiometry of about 1,200 protein molecules per VLP, slightly lower than the 1,500 Gag molecules estimated previously for infectious RSV. By cryo-EM, the VLPs showed the characteristic morphology of immature retroviruses, with discernible regions of high density corresponding to the two domains of the CA protein. In spherically averaged density distributions, the mean radial distance to the density corresponding to the C-terminal domain of CA was 33 nm, considerably smaller than that of equivalent human immunodeficiency virus type 1 particles. Deletions of the distal portion of NC, including the second Zn-binding motif, had little effect on assembly, but deletions including the charged residues between the two Zn-binding motifs abrogated assembly. Mutation of the cysteine and histidine residues in the first Zn-binding motif to alanine did not affect assembly, but mutation of the basic residues between the two Zn-binding motifs, or of the basic residues in the N-terminal portion of NC, abrogated assembly. Together, these findings establish VLPs as a good model for immature virions and establish a foundation for dissection of the interactions that lead to assembly.In retroviruses, the Gag polyprotein directs the assembly and budding of virions from the plasma membrane. Even in the absence of other viral proteins, expression of Gag leads to budding of particles resembling real virions. In wild-type viruses, Gag is cleaved late in the budding process by the viral protease (PR) to yield the mature proteins MA, CA, and NC that are common to all retroviruses plus other small proteins or peptides particular to the retrovirus species. For most retroviruses, including human immunodeficiency virus type 1 (HIV-1), Rous sarcoma virus (RSV), and murine leukemia virus (MuLV), assembly and budding occur concomitantly. These processes are not obligatorily coupled, however, since for the B-and D-type viruses assembly of immature viral cores takes place in the cytoplasm, followed by transport of the intact cores to the membrane and subsequent envelopment and proteolytic maturation. From deletion analyses, it appears that budding is dependent on the function of three short amino acid sequences in Gag, sometimes called assembly domains. The M (membrane...

Colorectal cancer is the third common cancer in this world, accounting for more than 1 million cases each year. However, detailed etiology and mechanism of colorectal cancer have not been fully understood. For example, cyclooxygenase-2 (COX-2) and its product prostaglandin E 2 (PGE 2) have been closely linked to its occurrence, progression and prognosis. However, the mechanisms on how COX-2 and PGE 2-mediate the pathogenesis of colorectal cancer are obscure. In this review, we have summarized recent advances in studies of pathogenesis and control in colorectal cancer to assist further advances in the research for the cure of the cancer. In addition, the knowledge gained may also guide the audiences for reduction of the risk and control of this deadly disease.

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Background Although maternal deaths are rare in developed regions, the morbidity associated with severe postpartum hemorrhage (SPPH) remains a major problem. To determine the prevalence and risk factors of SPPH, we analyzed data of women who gave birth in Guangzhou Medical Centre for Critical Pregnant Women, which received a large quantity of critically ill obstetric patients who were transferred from other hospitals in Southern China. Methods In this study, we conducted a retrospective case-control study to determine the prevalence and risk factors for SPPH among a cohort of women who gave birth after 28 weeks of gestation between January 2015 and August 2019. SPPH was defined as an estimated blood loss ≥1000 mL and total blood transfusion≥4 units. Logistic regression analysis was used to identify independent risk factors for SPPH. Results SPPH was observed in 532 mothers (1.56%) among the total population of 34,178 mothers. Placenta-related problems (55.83%) were the major identified causes of SPPH, while uterine atony without associated retention of placental tissues accounted for 38.91%. The risk factors for SPPH were maternal age < 18 years (adjusted OR [aOR] = 11.52, 95% CI: 1.51–87.62), previous cesarean section (aOR = 2.57, 95% CI: 1.90–3.47), history of postpartum hemorrhage (aOR = 4.94, 95% CI: 2.63–9.29), conception through in vitro fertilization (aOR = 1.78, 95% CI: 1.31–2.43), pre-delivery anemia (aOR = 2.37, 95% CI: 1.88–3.00), stillbirth (aOR = 2.61, 95% CI: 1.02–6.69), prolonged labor (aOR = 5.24, 95% CI: 3.10–8.86), placenta previa (aOR = 9.75, 95% CI: 7.45–12.75), placenta abruption (aOR = 3.85, 95% CI: 1.91–7.76), placenta accrete spectrum (aOR = 8.00, 95% CI: 6.20–10.33), and macrosomia (aOR = 2.30, 95% CI: 1.38–3.83). Conclusion Maternal age < 18 years, previous cesarean section, history of PPH, conception through IVF, pre-delivery anemia, stillbirth, prolonged labor, placenta previa, placental abruption, PAS, and macrosomia were risk factors for SPPH. Extra vigilance during the antenatal and peripartum periods is needed to identify women who have risk factors and enable early intervention to prevent SPPH.

GS-9160 is a novel and potent inhibitor of human immunodeficiency virus type 1 (HIV-1) integrase (IN) thatspecifically targets the process of strand transfer. It is an authentic inhibitor of HIV-1 integration, since treatment of infected cells results in an elevation of two-long terminal repeat circles and a decrease of integration junctions. GS-9160 has potent and selective antiviral activity in primary human T lymphocytes producing a 50% effective concentration (EC 50 ) of ϳ2 nM, with a selectivity index (50% cytotoxic concentration/ EC 50 ) of ϳ2,000. The antiviral potency of GS-9160 decreased by 6-to 10-fold in the presence of human serum. The antiviral activity of GS-9160 is synergistic in combination with representatives from three different classes of antiviral drugs, namely HIV-1 protease inhibitors, nonnucleoside reverse transcriptase inhibitors, and nucleotide reverse transcriptase inhibitors. Viral resistance selections performed with GS-9160 yielded a novel pattern of mutations within the catalytic core domain of IN; E92V emerged initially, followed by L74M. While E92V as a single mutant conferred 12-fold resistance against GS-9160, L74M had no effect as a single mutant. Together, these mutations conferred 67-fold resistance to GS-9160, indicating that L74M may potentiate the resistance caused by E92V. The pharmacokinetic profile of GS-9160 in healthy human volunteers revealed that once-daily dosing was not likely to achieve antiviral efficacy; hence, the clinical development of this compound was discontinued.After human immunodeficiency virus type 1 (HIV-1) entry and uncoating, the viral RNA is reverse transcribed by the viral reverse transcriptase into a double-stranded linear DNA. Both ends of this linear DNA are then processed at the 3Ј termini by the integrase (IN) enzyme. Specifically, IN removes a dinucleotide from each 3Ј terminus through a reaction referred to as 3Ј processing. The IN-DNA complex is then transported into the nucleus where IN performs concerted integration of both viral DNA ends into host chromosomal DNA by a reaction referred to as strand transfer. The integration of viral DNA into host chromosomal DNA is essential for HIV-1 replication, making the inhibition of HIV-1 IN function an attractive antiviral strategy (9,35,36,42).Historically, treatment of individuals infected with HIV-1 has relied on agents targeting two of the viral enzymes, reverse transcriptase and protease. Despite important clinical results achieved through the use of combinations of these agents, the continuous emergence of drug resistance remains a significant problem which fuels the need to discover novel drugs targeting other steps of the HIV-1 life cycle.