Destabilization of the TAR hairpin affects the structure and function of the HIV-1 leader RNA

The TAR hairpin of the human immunodeficiency virus type 1 (HIV-1) RNA genome is essential for virus replication. TAR forms the binding site for the transcriptional trans-activator protein Tat and multiple additional TAR functions have been proposed. We previously constructed an HIV-1 variant in which the TAR-Tat transcription control mechanism is replaced by the components of the Tet-ON regulatory system. In this context, the surprising finding was that TAR can be truncated or even deleted, but partial TAR deletions that destabilize the stem structure cause a severe replication defect. In this study, we demonstrate that the HIV-1 RNA genome requires a stable hairpin at its 5′-end because unpaired TAR sequences affect the proper folding of the untranslated leader RNA. Consequently, multiple leader-encoded functions are affected by partial TAR deletions. Upon evolution of such mutant viruses, the replication capacity was repaired through the acquisition of additional TAR mutations that restore the local RNA folding, thus preventing the detrimental effect on the leader conformation

Flexibility@Work 2013: yearly report on flexible labor and employment

There is no clear evidence that the strong growth in the share of flexible labor relations between 2002 and 2007 points at a worldwide trend towards a larger share of flexible labor at the expense of traditional open-ended labor contracts. The growth in flexible labor varies too much between countries and periods to draw such a conclusion. In most countries in Europe, in North America and Japan, the share of flexible labor has declined during the recent economic recession that started after 2007. There is also no structural trade-off between different forms of (formal) flexible labor. Observations in Europe suggest that growth or decline of different types of flexible labor can be attributed to changes in both local societal and economic structures and in institutions and legislation. Growth of flexible labor appears mainly in countries where the labor participation is increasing while it is declining where labor participation is relatively low or stagnating. This suggests an important role for flexible labor for new non-traditional labor market participants to enter the labor market. At the same time, there is a strong correlation between the share of flexible labor and economic growth, particularly with respect to fixed-term contracts and agency work. Flexible labor is the first form of employment effected by a decline in labor demand in an economic crisis, particularly when flexible workers are younger and lower educated. But at the same time, flexible work will be the first type of employment that recovers when the economy stabilizes after a crisis. The opportunity to offer flexible work may even accelerate economic growth. Therefore, a further growth in flexible work can be expected once the economies in most western countries start to grow significantly again. Agency work in particular has grown in nearly all markets over the last decade, which does indicate a structural component of growth of agency work in the modern labor market apart from the business cycle

Giant Quantum Reflection of Neon Atoms from a Ridged Silicon Surface

The specular reflectivity of slow, metastable neon atoms from a silicon surface was found to increase markedly when the flat surface was replaced by a grating structure with parallel narrow ridges. For a surface with ridges that have a sufficiently narrow top, the reflectivity was found to increase more than two orders of magnitude at the incident angle of 10 mRad from the surface. The slope of the reflectivity vs the incident angle near zero was found to be nearly an order of magnitude smaller than that of a flat surface. A grating with 6.5% efficiency for the first-order diffraction was fabricated by using the ridged surface structure.Comment: 5 pages, 4 figures. To be published in J. Phys. Soc. Jp

SIVdrl detection in captive mandrills: are mandrills infected with a third strain of simian immunodeficiency virus?

A pol-fragment of simian immunodeficiency virus (SIV) that is highly related to SIVdrl-pol from drill monkeys (Mandrillus leucophaeus) was detected in two mandrills (Mandrillus sphinx) from Amsterdam Zoo. These captivity-born mandrills had never been in contact with drill monkeys, and were unlikely to be hybrids. Their mitochondrial haplotype suggested that they descended from founder animals in Cameroon or northern Gabon, close to the habitat of the drill. SIVdrl has once before been found in a wild-caught mandrill from the same region, indicating that mandrills are naturally infected with a SIVdrl-like virus. This suggests that mandrills are the first primate species to be infected with three strains of SIV: SIVmnd1, SIVmnd2, and SIVdrl