Cell type-specific regulation of choline acetyltransferase gene expression - Role of the neuron-restrictive silencer element and cholinergic-specific enhancer

This study demonstrates the presence of positive and negative regulatory elements within a 2336-base pair-long region of the rat choline acetyltransferase (ChAT) gene promoter that cooperate to direct cell type-specific expression in cholinergic cells. A 21-base pair-long neuron-restrictive silencer element (NRSE) was identified in the proximal part of this region. This element was recognized by the neuron-restrictive silencer factor (NRSF), previously shown to regulate expression of other neuron-specific genes. The ChAT NRSE was inactive in both cholinergic and non-cholinergic neuronal cells, but repressed expression from a heterologous promoter in non-neuronal cells. Specific deletion of this element allowed ChAT gene promoter activity in non-neuronal cells, and overexpression of NRSF repressed ChAT gene promoter activity in cholinergic cells. The distal part of the ChAT gene promoter showed cholinergic-specific enhancing activity, which stimulated promoter activity in cholinergic cells, but was inactive in non-cholinergic neuronal and non-neuronal cells. This enhancer region suppressed the activity of the ChAT NRSE in cholinergic cells, even after NRSF overexpression. Thus, at least two kinds of regulatory elements cooperate to direct ChAT gene expression to cholinergic neurons, namely a neuron-restrictive silencer element and a cholinergic-specific enhancer

Monetary policy and inflation persistence in the Eurozone

The primary goal of the European Central Bank’s (ECB) monetary policy is to achieve price stability. Whereas during the 1980s and 1990s there was a rapid and strong convergence in terms of price differential among the Euro countries, particularly in those countries with higher inflation rates in the past, single monetary policy has proved to be quite inefficient in continuing this trend and has not achieved further reductions in inflation rate differentials within the euro zone. Since the ECB sets the official interest rate according to the average inflation of the euro area, the persistence of such price differentials within the area would mean that the “one size interest rate policy” would not fit all. This paper studies empirically the inflation rate differentials and their persistence in some currency unions with the aim to draw some conclusions for the working of the ECB monetary policy. KEYWORDS: monetary policy; inflation persistence; currency unions

Galaxy destruction and diffuse light in clusters

Deep images of the Centaurus and Coma clusters reveal two spectacular arcs of diffuse light that stretch for over 100 kpc, yet are just a few kpc wide. At a surface brightness of m_b \sim 27-28th arcsec^-2, the Centaurus arc is the most striking example known of structure in the diffuse light component of a rich galaxy cluster. We use numerical simulations to show that the Centaurus feature can be reproduced by the tidal debris of a spiral galaxy that has been tidally disrupted by the gravitational potential of NGC 4709. The surface brightness and narrow dimensions of the diffuse light suggest that the disk was co-rotating with its orbital path past pericentre. Features this prominent in clusters will be relatively rare, although at fainter surface brightness levels the diffuse light will reveal a wealth of structure. Deeper imaging surveys may be able to trace this feature for several times its presently observed extent and somewhere along the tidal debris, a fraction of the original stellar component of the disk will remain bound, but transformed into a faint spheroidal galaxy. It should be possible to confirm the galactic origin of the Centaurus arc by observing planetary nebulae along its length with redshifts close to that of NGC 4709.Comment: Replaced with version accepted by MNRAS (Dec. 1999): Added missing reference (to pg. 4 & reference list). Section 3 shortened; removed three figures. Now 8 pages long, with 8 figures. Low resolution images included, high resolution version available at http://star-www.dur.ac.uk:80/~calcaneo/cenarc.htm