The authors' results indicate that quantifying the levels of survivin and its splice variants is useful for the prediction of the cell biological malignancy of gliomas, independent of their pathological features.

Summary Replication of the Escherichia coli chromosome is initiated synchronously from all origins (oriC) present in a cell at a fixed time in the cell cycle under given steady state culture conditions. A mechanism to ensure the cyclic initiation events operates through the chromosomal site, datA, which titrates exceptionally large amounts of the bacterial initiator protein, DnaA, to prevent overinitiation. Deletion of the datA locus results in extra initiations and altered temporal control of replication. There are many other sites on the E. coli chromosome that can bind DnaA protein, but the contribution of these sites to the control of replication initiation has not been investigated. In the present study, seven major DnaA binding sites other than datA have been examined for their influence on the timing of replication initiation. Disruption of these seven major binding sites, either individually or together, had no effect on the timing of initiation of replication. Thus, datA seems to be a unique site that adjusts the balance between free and bound DnaA to ensure that there is only a single initiation event in each bacterial cell cycle. Mutation either in the second or the third DnaA box (a 9 basepair DnaA‐binding sequence) in datA was enough to induce asynchronous and extra initiations of replication to a similar extent as that observed with the datA‐deleted strain. These DnaA boxes may act as cores for the cooperative binding of DnaA to the entire datA region.

The initiation of replication in Escherichia coli is negatively controlled by a mechanism referred to as 'initiator titration', a process by which the initiator protein, DnaA, is titrated to newly replicated binding sequences on the chromosome to reduce the initiation potential for replication. Initiator titration occurs predominantly at the datA locus that binds exceptionally large amounts of DnaA molecules to prevent aberrant initiations. We found that this was enabled by integration host factor (IHF). Within datA, there is a consensus IHF recognition sequence between the two DnaA recognition sequences (DnaA boxes) essential for its function. Binding of IHF to this site was demonstrated both in vitro and in vivo. Disruption of the core sequence in the consensus of the IHF-binding resulted in increased origin concentration as observed in ΔdatA cells. Furthermore, the number of DnaA molecules bound to datA was reduced in cells carrying a disruption in the IHF-binding core sequence. The IHF-binding site and the essential DnaA boxes had to be located at a proper distance and orientation to maintain the accurate initiation timing. Therefore, IHF is a unique element in the control of replication initiation that acts negatively at datA, while known to act as a positive regulator at oriC.

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~_ _ _The profile of generation and characteristics of splenic macrophages (MOs) which suppress the concanavalin A (Con A) mitogenic response of splenic T cells (designated as 'immunosuppressive MOs') in host CBA/JN mice during the course of Mycobacferium avium complex (MAC) infection were investigated. In MAC-infected mice, reductions in some cellular functions of host splenic T cells, such as the Con A mitogenic response and mixed leucocyte reaction, were seen around 2 weeks after challenge of organisms, and this was accompanied by appearance of immunosuppressive M a s in spleen cells. In this case, increase in immunosuppressive M a activity was seen in terms of both activity per spleen and activity per individual M(D. In this phase of the infection, MACinduced splenic MOs showed a markedly increased ability to produce reactive oxygen radicals in response to pborbol myristate acetate. Thus, the expression of suppressor activity of MAC-induced MOs Seems to be closely linked to their activated state. A large proportion of the immunosuppressive M a s exhibited suppressor activity dependent on prostaglandins and membrane functions related to microfilaments. It was also found that the generation of IL-2-reactive T cell populations in response to Con A was markedly inhibited by MAC-induced splenic MOs, whereas they caused no significant reduction in the IL-Zproducing ability of normal spleen cells.