Comparison of genetic behaviour of the transposable element Tam3 at two unlinked pigment loci in Antirrhinum majus

Summary In Antirrhinum majus the transposable element Tam3 has been described at two unlinked loci pallida and nivea, both of which are required for the production of anthocyanin pigment in flowers. In each case the element is inserted in the promoter region and gives a variegated phenotype. We show that the rate of Tam3 excision at both loci is greatly affected by temperature, being approximately 1000-fold higher at 15°C compared with 25°C. Tam3 is also controlled by an unlinked gene Stabiliser, which considerably reduces excision rate. We show that the high degree of sensitivity to temperature and Stabiliser is an intrinsic property of Tam3 which is not shared by an unrelated element, Tam1. The Tam3 insertion at nivea gives rise to a series of alleles which confer reduced pigmentation, novel spatial patterns and changed instability. These are probably a result of imprecise excision and rearrangements of the Tam3 element.     

The organization of DNA sequences in the mouse genome

Analysis of the organization of nucleotide sequences in mouse genome is carried out on total DNA at different fragment size, reannealed to intermediate value of Cot, by Ag⁺-Cs₂SO₄ density gradient centrifugation. — According to nuclease S-1 resistance and kinetic renaturation curves mouse genome appears to be made up of non-repetitive DNA (76% of total DNA), middle repetitive DNA (average repetition frequency 2×10⁴ copies, 15% of total DNA), highly repetitive DNA (8% of total DNA) and fold-back DNA (renatured density 1.701 g/ml, 1% of total DNA).— Non-repetitive sequences are intercalated with short middle repetitive sequences. One third of non-repetitive sequences is longer than 4500 nucleotides, another third is long between 1800 and 4500 nucleotides, and the remainder is shorter than 1800 nucleotides. —Middle repetitive sequences are transcribed in vivo. The majority of the transcribed repeated sequences appears to be not linked to the bulk of non-repeated sequences at a DNA size of 1800 nucleotides. — The organization of mouse genome analyzed by Ag⁺-Cs₂SO₄ density gradient of reannealed DNA appears to be substantially different than that previously observed in human genome using the same technique.     

Computational modelling of the binding of arachidonic acid to the human monooxygenase CYP2J2

An experimentally determined structure for human CYP2J2—a member of the cytochrome P450 family with significant and diverse roles across a number of tissues—does not yet exist. Our understanding of how CYP2J2 accommodates its cognate substrates and how it might be inhibited by other ligands thus relies on our ability to computationally predict such interactions using modelling techniques. In this study we present a computational investigation of the binding of arachidonic acid (AA) to CYP2J2 using homology modelling, induced fit docking (IFD) and molecular dynamics (MD) simulations. Our study reveals a catalytically competent binding mode for AA that is distinct from a recently published study that followed a different computational pipeline. Our proposed binding mode for AA is supported by crystal structures of complexes of related enzymes to inhibitors, and evolutionary conservation of a residue whose role appears essential for placing AA in the right site for catalysis.

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Graphical Abstract Arachidonic acid docked in the active site of CYP2J2 assumes a catalytically competent binding mode stabilised by hydrogen bonds to Arg117

     

Interaction between catalytically inactive calpain and calpastatin. Evidence for its occurrence in stimulated cells

Conformational changes in the calpain molecule following interaction with natural ligands can be monitored by the binding of a specific monoclonal antibody directed against the catalytic domain of the protease. None of these conformational states showed catalytic activity and probably represent intermediate forms preceding the active enzyme state. In its native inactive conformation, calpain shows very low affinity for this monoclonal antibody, whereas, on binding to the ligands Ca(2+), substrate or calpastatin, the affinity increases up to 10-fold, with calpastatin being the most effective. This methodology was also used to show that calpain undergoes similar conformational changes in intact cells exposed to stimuli that induce either a rise in intracellular [Ca(2+)] or extensive diffusion of calpastatin into the cytosol without affecting Ca(2+) homeostasis. The fact that the changes in the calpain state are also observed under the latter conditions indicates that calpastatin availability in the cytosol is the triggering event for calpain-calpastatin interaction, which is presumably involved in the control of the extent of calpain activation through translocation to specific sites of action.     

Protection by herpes simplex virus glycoprotein D against Fas-mediated apoptosis: role of nuclear factor kappaB

Signals involved in protection against apoptosis by herpes simplex virus 1 (HSV-1) were investigated. Using U937 monocytoid cells as an experimental model, we have demonstrated that HSV-1 rendered these cells resistant to Fas-induced apoptosis promptly after infection. UV-inactivated virus as well as the envelope glycoprotein D (gD) of HSV-1, by itself, exerted a protective effect on Fas-induced apoptosis. NF-kappaB was activated by gD, and protection against Fas-mediated apoptosis by gD was abolished in cells stably transfected with a dominant negative mutant I-kappaBalpha, indicating that NF-kappaB activation plays a role in the antiapoptotic activity of gD in our experimental model. Moreover, NF-kappaB-dependent protection against Fas-mediated apoptosis was associated with decreased levels of caspase-8 activity and with the up-regulation of intracellular antiapoptotic proteins.     

Head and Neck Veins of the Mouse. A Magnetic Resonance,Micro Computed Tomography and High Frequency Color Doppler Ultrasound Study

To characterize the anatomy of the venous outflow of the mouse brain using different imaging techniques. Ten C57/black male mice (age range: 7-8 weeks) were imaged with high-frequency Ultrasound, Magnetic Resonance Angiography and ex-vivo Microcomputed tomography of the head and neck. Under general anesthesia, Ultrasound of neck veins was performed with a 20MHz transducer; head and neck Magnetic Resonance Angiography data were collected on 9.4T or 7T scanners, and ex-vivo Microcomputed tomography angiography was obtained by filling the vessels with a radiopaque inert silicone rubber compound. All procedures were approved by the local ethical committee. The dorsal intracranial venous system is quite similar in mice and humans. Instead, the mouse Internal Jugular Veins are tiny vessels receiving the sigmoid sinuses and tributaries from cerebellum, occipital lobe and midbrain, while the majority of the cerebral blood, i.e. from the olfactory bulbs and fronto-parietal lobes, is apparently drained through skull base connections into the External Jugular Vein. Three main intra-extracranial anastomoses, absent in humans, are: 1) the petrosquamous sinus, draining into the posterior facial vein, 2) the veins of the olfactory bulb, draining into the superficial temporal vein through a foramen of the frontal bone 3) the cavernous sinus, draining in the External Jugular Vein through a foramen of the sphenoid bone. The anatomical structure of the mouse cranial venous outflow as depicted by Ultrasound, Microcomputed tomography and Magnetic Resonance Angiography is different from humans, with multiple connections between intra- and extra- cranial veins.