Mutations in the putative dimer-dimer interfaces of the measles virus hemagglutinin head domain affect membrane fusion triggering.

Measles virus (MV), an enveloped RNA virus belonging to the Paramyxoviridae family, enters the cell through membrane fusion mediated by two viral envelope proteins, an attachment protein hemagglutinin (H) and a fusion (F) protein. The crystal structure of the receptor-binding head domain of MV-H bound to its cellular receptor revealed that the MV-H head domain forms a tetrameric assembly (dimer of dimers), which occurs in two forms (forms I and II). In this study, we show that mutations in the putative dimer-dimer interface of the head domain in either form inhibit the ability of MV-H to support membrane fusion, without greatly affecting its cell surface expression, receptor binding, and interaction with the F protein. Notably, some anti-MV-H neutralizing monoclonal antibodies are directed to the region around the dimer-dimer interface in form I rather than receptor-binding sites. These observations suggest that the dimer-dimer interactions of the MV-H head domain, especially that in form I, contribute to triggering membrane fusion, and that conformational shift of head domain tetramers plays a role in the process. Furthermore, our results indicate that although the stalk and transmembrane regions may be mainly responsible for the tetramer formation of MV-H, the head domain alone can form tetramers, albeit at a low efficiency.

Inhibition of telomerase recruitment and cancer cell death.

Continued proliferation of human cells requires maintenance of telomere length, usually accomplished by telomerase. Telomerase is recruited to chromosome ends by interaction with a patch of amino acids (the TEL patch, for TPP1 glutamate (E) and leucine (L)-rich patch) on the surface of telomere protein TPP1. In previous studies, interruption of this interaction by mutation prevented telomere extension in HeLa cells, but the cell culture continued to grow. We now show that the telomerase inhibitor BIBR1532 acts together with TEL patch mutations to inhibit the growth of HeLa cell lines and that apoptosis is a prominent mechanism of death of these cells. Survivor cells take over the population beginning around 40 days in culture. These cells no longer express the TEL patch mutant TPP1, apparently because of silencing of the expression cassette, a survival mechanism that would not be available to cancer cells. These results provide hope that inhibiting the binding of telomerase to the TEL patch of TPP1, perhaps together with a modest inhibition of the telomerase enzyme, could comprise an effective anticancer therapy for the ∼90% of human tumors that are telomerase-positive.

Sequence-dependent heterochromatin formation in the human malaria parasite Plasmodium falciparum.

The human malaria parasite Plasmodium falciparum represses transcription of the gene encoding AP2-G, which is the master regulator of germ cell differentiation, via heterochromatin condensation following histone H3 lysine 9 trimethylation (H3K9me3). Although H3K9me3-marked heterochromatin is typically constitutive and its establishment depends on the RNA interference (RNAi) pathway in fission yeast centromeres, malaria parasites lack molecular members essential for RNAi. We developed a strategy to assess heterochromatin establishment on artificial chromosomes introduced into P. falciparum. We show that a particular DNA sequence in the AP2-G promoter is able to induce de novo H3K9me3 nucleosome deposition. In addition, we also found that the AP2-G promoter contains a distinct element required in maintenance of the repression memory. Thus, we speculate that malaria parasites have evolutionarily acquired a sequence-dependent establishment system of non-constitutive, i.e. facultative, H3K9me3-marked heterochromatin.

Factors Contributing to the Prognosis after Second-line Therapy with Ramucirumab in Advanced Hepatocellular Carcinoma.

Objective Multiple therapeutic agents exist for advanced hepatocellular carcinoma (HCC), but prognostic factors in second-line and subsequent therapies are unclear. Ramucirumab is a molecular-targeted agent effective against hepatocytes with alpha-fetoprotein (AFP) >400 ng/mL after sorafenib failure. We examined the prognostic factors and efficacy of ramucirumab with prior therapy other than sorafenib. Methods In our retrospective multicenter study, 33 patients were treated with ramucirumab for HCC with prior therapy other than sorafenib, including 1 patient who received 2 lines of ramucirumab. We analyzed background factors, liver reserve, the prognosis, and treatment duration and efficacy. Results The median albumin-bilirubin (ALBI) value showed little change during ramucirumab treatment. The ALBI value improved in 32% of patients, and their prognoses were better than in those who did not improve. Response and efficacy rates were not as high as those in the REACH-2 study but were similar when limited to patients with 2,500 ng/mL AFP. Thirteen patients received further treatment after ramucirumab failure and they had a significantly better prognosis from ramucirumab administration and also had a significantly better prognosis from the start of the first tyrosine kinase inhibitor than who did not received further treatment. In univariate and multivariate analyses of prognostic factors, the continuation of treatment with another drug after ramucirumab failure and a good ALBI value at initiation were significant. The presence of a ramucirumab response and treatment duration were not associated with the prognosis. A good ALBI value at initiation and ALBI value improvement during treatment were also identified as independent factors associated with eligibility for further treatment after ramucirumab failure. The treatment line did not correlate with the availability of treatment with another drug after treatment failure. Conclusions ALBI value improvement with ramucirumab treatment allows for subsequent treatment after failure and an improved overall prognosis.

Radial mycotic aneurysm complicated with infective endocarditis caused by Streptococcus sanguinis.

Peripheral mycotic aneurysm is a rare complication of infective endocarditis. We herein report the case of a 61-year-old man with a mycotic aneurysm in the left brachial artery, that appeared during treatment with antibiotics against infective endocarditis caused by Streptococcus sanguinis. After confirming the collateral blood flow on arteriography, we resected the aneurysm and performed valvuloplasty, annuloplasty and coronary artery bypass grafting. The patient has been in good condition without complications, such as motor dysfunction or neuropathy.