The HIV-1 Tat protein stimulates viral gene expression by recruiting human transcription elongation complexes containing P-TEFb, AFF4, ELL2, and ENL or AF9 to the viral promoter, but the molecular organization of these complexes remains unknown. To establish the overall architecture of the HIV-1 Tat elongation complex, we mapped the binding sites that mediate complex assembly in vitro and in vivo. The AFF4 protein emerges as the central scaffold that recruits other factors through direct interactions with short hydrophobic regions along its structurally disordered axis. Direct binding partners CycT1, ELL2, and ENL or AF9 act as bridging components that link this complex to two major elongation factors, P-TEFb and the PAF complex. The unique scaffolding properties of AFF4 allow dynamic and flexible assembly of multiple elongation factors and connect the components not only to each other but also to a larger network of transcriptional regulators.paused RNA polymerase II | intrinsically disordered proteins | super elongation complex | MLL-fusion complex R NA polymerase II (Pol II) activity is tightly regulated throughout the steps of eukaryotic transcription. Each stage-initiation, clearance from the promoter, elongation, and termination-is licensed by specific factors that serve as checkpoints (1-4). Pol II transcription downstream of the promoter also involves intricate crosstalk between elongation and posttranscriptional events, such as splicing (5-7).

The aim of the study was to evaluate the effect of nitrogen (N) and sulphur (S) fertilizer on grain yield of spring wheat and its technological quality. A field experiment (2009-2011) was conducted in south-eastern Poland on Cambisols. The experiment included 2 factors: N fertilization (0, 40, 80, 120 kg/ha) and S fertilization (0, 50 kg/ha). The experiment showed that spring wheat cv. Tybalt exhibited a positive reaction of N and S fertilization on grain yield, which was the highest at the application of 80 kg N/ha (5.40 t/ha), increasing by 1.30 t/ha (13.1%) with respect to the control. S fertilization increased grain yield by 3.58%. S application increased significantly the content of gluten by 3.2%, cysteine by 6.0% and methionine by 16.5%. The most beneficial effect on the content of N, S, total protein, gluten, cysteine and methionine was observed for N application a rate of 80 kg/ha and for S at a rate of 50 kg/ha. Positive correlation was found between the content of S in grain and grain yield (r = 0.73). Significant correlations were found also between grain yield and all other quality characteristics except for N and starch content.

SummarySuccinic acid is an important C4‐building chemical platform for many applications. A novel succinic acid‐producing bacterial strain was isolated from goat rumen. Phylogenetic analysis based on the 16S rRNA sequence and physiological analysis indicated that the strain belongs to the genus Enterobacter. This is the first report of a wild bacterial strain from the genus Enterobacter that is capable of efficient succinic acid production. Co‐fermentation of glycerol and lactose significantly improved glycerol utilization under anaerobic conditions, debottlenecking the utilization pathway of this valuable biodiesel waste product. Succinic acid production reached 35 g l−1 when Enterobacter sp. LU1 was cultured in medium containing 50 g l−1 of glycerol and 25 g l−1 of lactose as carbon sources.

The study concerns the measurement of the technical efficiency of agriculture in the 27 European Union (EU) countries in 2010. The studies were conducted based on the result-oriented DEA method assuming variable advantages of scale. Moreover, in the study, the factors affecting technical efficiency were identified, and the econometric modelling of their impact was performed with the use of the Tobit model. The studies indicate that across the 27 EU Member States, the level of the technical efficiency of agriculture is diverse, and the difference between the states with the highest and the lowest efficiencies is 40%. Cyprus, Denmark, Greece, France, Spain, the Netherlands, Luxembourg, Italy and Malta were identified as the countries with the thoroughly technically efficient agriculture. In turn, the least technically efficient agriculture is observed for the Czech Republic, Lithuania, Hungary, Ireland, Latvia and Slovakia. Taking into account the factors determining the technical agriculture efficiency, it should be noted that the stimulants have proven to be such factors as: the soil quality, the age of the head of the household and the surcharges for investments. In turn, the size of the farm appeared to be irrelevant from the viewpoint of the technical efficiency of the agricultural sector.

SUMMARYAlthough the effect of saponins or saponin-containing plants on rumen microorganisms and rumen fermentation has been intensively investigated, this issue still requires special attention. Many of the phenomena occurring in the rumen related to dietary saponin supplementation are still not fully understood. Saponaria officinalis is a triterpenoid saponin-containing plant; thus, the aim of the present study was to evaluate the effect of S. officinalis L. powdered root, methanolic extract of the S. officinalis root (SOR) and the effect of the separated fractions (polysaccharides, saponins and phenolics) of S. officinalis on rumen methanogenesis, microbial population and rumen fermentation characteristics in an in vitro batch culture fermentation system. The powdered root (raw plant material) and S. officinalis extract (SOE) decreased in vitro methane production and consequently reduced the microbial population in a dose-dependent manner. The inhibition of methanogenesis was accompanied by changes in the volatile fatty acids profile. In vitro dry matter digestibility was not affected by any of the secondary compounds applied. The highest applied doses of SOE caused a higher reduction in methanogenesis (33·5 v. 14·4%) than the highest doses of powdered root form. Such results suggest that the basic components of the SOR could interact with phytochemicals or that the phytochemicals became physically less available for microbiota, resulting in a decreased antimethanogenic activity of the powdered root v. the extract. Among all the fractions selected, the saponin fraction exerted the greatest impact on ruminal fermentation. In conclusion, saponins decreased methane production by 29% in comparison with the control. This decrease was related to the reduction in protozoa and methanogen counts. It is proposed that S. officinalis has the potential to inhibit rumen methanogenesis without affecting rumen fermentation adversely.