E(y)2/Sus1 is required for blocking PRE silencing by the Wari insulator in Drosophila melanogaster

Chromatin insulators affect interactions between promoters and enhancers/silencers and function as barriers to the spread of repressive chromatin. Recently, we have found an insulator, named Wari, located on the 3′ side of the white gene. Here, we show that the previously identified 368-bp core of this insulator is sufficient for blocking Polycomb response element-mediated silencing. Although Wari does not contain binding sites for known insulator proteins, the E(y)2 and CP190 proteins bind to Wari as well as to the Su(Hw)-containing insulators in vivo. It may well be that these proteins are recruited to the insulator by as yet unidentified DNA-binding protein. Partial inactivation of E(y)2 in a weak e(y)2 ^u1 mutation impairs only the anti-silencing but not the enhancer-blocking activity of the Wari insulator. Thus, the E(y)2 protein in different Drosophila insulators serves to protect gene expression from silencing.     

Structural basis for norovirus inhibition and fucose mimicry by citrate

Human noroviruses bind with their capsid-protruding domains to histo-blood-group antigens (HBGAs), an interaction thought to direct their entry into cells. Although human noroviruses are the major cause of gastroenteritis outbreaks, development of antivirals has been lacking, mainly because human noroviruses cannot be cultivated. Here we use X-ray crystallography and saturation transfer difference nuclear magnetic resonance (STD NMR) to analyze the interaction of citrate with genogroup II (GII) noroviruses. Crystals of citrate in complex with the protruding domain from norovirus GII.10 Vietnam026 diffracted to 1.4 Å and showed a single citrate bound at the site of HBGA interaction. The citrate interaction was coordinated with a set of capsid interactions almost identical to that involved in recognizing the terminal HBGA fucose, the saccharide which forms the primary conserved interaction between HBGAs and GII noroviruses. Citrate and a water molecule formed a ring-like structure that mimicked the pyranoside ring of fucose. STD NMR showed the protruding domain to have weak affinity for citrate (460 μM). This affinity, however, was similar to the affinities of the protruding domain for fucose (460 μM) and H type 2 trisaccharide (390 μM), an HBGA shown previously to be specifically recognized by human noroviruses. Importantly, competition STD NMR showed that citrate could compete with HBGA for norovirus binding. Together, the results suggest that citrate and other glycomimetics have the potential to block human noroviruses from binding to HBGAs.     

Functional properties of the WNT11 new isoform, expressed in colon carcinoma cell line HT29

Colon carcinoma is a common type of neoplastic transformation. Mechanisms of its establishment and progression have been studying for several decades. Aberrant activation of the canonical Wnt signaling is frequently observed in colon carcinoma cells. Moreover, expression of the "noncanonical" Wnt ligands is also detected in this type of cancer. However, the implication of the noncanonical Wnt signaling in carcinogenesis and colorectal cancer (CRC) progression is still unclear. Here, to elucidate the characteristic features of the noncanonical Wnt signaling activation in CRC the expression of the "noncanonical" ligand hWnt11 has been studied. It was shown for the first time that expression of the hWnt11 in CRC is accompanied by the alternative splicing. The new hWnt11 isoform (hWnt11sp3) has been identified. Unlike to hWnt11, this isoform is not secreted and lacks the ability to inhibit the canonical Wnt signaling. Considering the canonical Wnt signaling inhibiting activity of hWnt11, different functional properties of the ligand and its isoform may reflect a special role of the alternative splicing in carcinogenesis and tumor progression. Thus, due to the difference in their functional properties an existence of several Wnt isoforms should be taken into account for the investigation of the role of Wnt ligands.