Phage Mu transposes by two distinct pathways depending on the specific stage of its life cycle. A common θ strand transfer intermediate is resolved differentially in the two pathways. During lytic growth, the θ intermediate is resolved by replication of Mu initiated within the flanking target DNA; during integration of infecting Mu, it is resolved without replication, by removal and repair of DNA from a previous host that is still attached to the ends of the incoming Mu genome. Our studies show that the cryptic endonuclease activity reported for the isolated C-terminal domain of the transposase MuA, which is not observed in the full-length protein or in the assembled transpososome in vitro, is required in vivo for removal of the attached host DNA or “5’flap” after the infecting Mu genome has integrated into the E. coli chromosome. I have identified additional phage and host factors required for flap removal in vivo, which include an early Mu protein called Ner, and the E. coli protein ClpX. Ner regulates bidirectional transcription through the Mu transposition enhancer, while ClpX, a molecular chaperone, is known to interact with the C-terminus of MuA to remodel the transpososome for replication. The transpososome is a multi-subunit MuA complex assembled on the two paired ends of Mu. The enhancer DNA segment serves as an essential scaffold for transpososome assembly, and remains stably associated with θ strand transfer MuA complexes. I hypothesize that Ner-regulated transcription through the enhancer remodels transpososome conformation in the presence of ClpX, promoting activation of the MuA endonuclease, which resects flanking DNA during the repair pathway of Mu transposition. / text

The objective of this research is to explore the information content of repeat-pass cross-track Interferometric SAR (InSAR) with regard to snow, in particular Snow Water Equivalent (SWE) and snow depth. The study is an outgrowth of earlier snow cover modeling and radar interferometry experiments at Schefferville, Quebec, Canada and elsewhere which has shown that for reasons of loss of coherence repeat-pass InSAR is not useful for the purpose of snow cover mapping, even when used in differential InSAR mode. Repeat-pass cross-track InSAR would overcome this problem. As at radar wavelengths dry snow is transparent, the main reflection is at the snow/ground interface. The high refractive index of ice creates a phase delay which is linearly related to the water equivalent of the snow pack. When wet, the snow surface is the main reflector, and this enables measurement of snow depth. Algorithms are elaborated accordingly. Field experiments were conducted at two sites and employ two different types of digital elevation models (DEM) produced by means of cross track InSAR. One was from the Shuttle Radar Topography Mission digital elevation model (SRTM DEM), flown in February 2000. It was compared to the photogrammetrically produced Canadian Digital Elevation Model (CDEM) to examine snow-related effects at a site near Schefferville, where snow conditions are well known from half a century of snow and permafrost research. The second type of DEM was produced by means of airborne cross track InSAR (TOPSAR). Several missions were flown for this purpose in both summer and winter conditions during NASA's Cold Land Processes Experiment (CLPX) in Colorado, USA. Differences between these DEM's were compared to snow conditions that were well documented during the CLPX field campaigns. The results are not straightforward. As a result of automated correction routines employed in both SRTM and AIRSAR DEM extraction, the snow cover signal is contaminated. Fitting InSAR DEM's to known topography distorts the snow information, just as the snow cover distorts the topographic information. The analysis is therefore mostly qualitative, focusing on particular terrain situations. At Schefferville, where the SRTM was adjusted to known lake levels, the expected dry-snow signal is seen near such lakes. Mine pits and waste dumps not included in the CDEM are depicted and there is also a strong signal related to the spatial variations in SWE produced by wind redistribution of snow near lakes and on the alpine tundra. In Colorado, cross-sections across ploughed roads support the hypothesis that in dry snow the SWE is measurable by differential InSAR. They also support the hypothesis that snow depth may be measured when the snow cover is wet. Difference maps were also extracted for a 1 km2 Intensive Study Area (ISA) for which intensive ground truth was available. Initial comparison between estimated and observed snow properties yielded low correlations which improved after stratification of the data set.In conclusion, the study shows that snow-related signals are measurable. For operational applications satellite-borne cross-track InSAR would be necessary. The processing needs to be snow-specific with appropriate filtering routines to account for influences by terrain factors other than snow.

Mitochondria are some of the most complex organelles of eukaryotic cell. They have their own genome and transcriptional apparatus and maintain several key cellular functions. A substantial part of cellular energetic metabolism happens in the mitochondria, as well as formation of iron-sulfur complexes, synthesis of several key molecules and they are also the essential organelles for the apoptotic pathway. In order to maintain the quality of proteins in their oxidative environment, mitochondria have developed a complex system of proteases that reaches all the mitochondrial compartments that degrade damaged proteins and thus promote mitochondrial turnover. The aim of this work was to characterise function of ClpP subunit of ClpXP matrix protease, which role was not yet extensively investigated in human cells. Therefore, we used RNA-interference to silence expression of ClpP in HEK 293 cells and then we performed rescue experiment during which we reintroduced ClpP in cells. Our results show that the ClpP subunit does not actively participate in apoptotic pathway, nevertheless it is essential for correct assembly of all the respiratory complexes as well as the quality of mitochondria itself. We have also shown that the system of mitochondrial proteases is highly functional and that a lack of ClpP...