232 research outputs found
The strong enhancer element in the immediate early region of the human cytomegalovirus genome
The human cytomegalovirus (HCMV), a
member of the herpesvirus group, was found to
possess a strong transcription enhancer in the
immediate early gene region. Co-transfection
of enhancerless SV40 DNA with randomly fragmented
HCMV DNA yielded two SV40-like recombinant
viruses , each containing HCMV DNA fragments that
were substituting for the missing SV40 enhancer.
The two inserts , 341 and 262 bp in length , are
overlapping segments of genuine viral DNA representing
part of the 5'flanking region of the
major immedistte early gene i n HCMV. Studies
with deletion mutants showed that different nonoverlapping
subsets of the HCMV enhancer region
can substitute for the 72 bp repeats of SV40.
Transient expression assays indicated that the
HCMV enhancer is significantly stronger than the
SV40 element, activating cis-linked heterologous
promoters in a wide spectrum of cultured cells.
It appears that the HCMV enhancer is positively
regulated by viral immediate early genes
Receptor binding proteins of Listeria monocytogenes bacteriophages A118 and P35 recognize serovar-specific teichoic acids
Adsorption of a bacteriophage to the host requires recognition of a cell wall-associated receptor by a receptor binding protein (RBP). This recognition is specific, and high affinity binding is essential for efficient virus attachment. The molecular details of phage adsorption to the Gram-positive cell are poorly understood. We present the first description of receptor binding proteins and a tail tip structure for the siphovirus group infecting Listeria monocytogenes. The host-range determining factors in two phages, A118 and P35 specific for L. monocytogenes serovar 1/2 have been determined. Two proteins were identified as RBPs in phage A118. Rhamnose residues in wall teichoic acids represent the binding ligands for both proteins. In phage P35, protein gp16 could be identified as RBP and the role of both rhamnose and N-acetylglucosamine in phage adsorption was confirmed. Immunogold-labeling and transmission electron microscopy allowed the creation of a topological model of the A118 phage tail
Listeria monocytogenes tyrosine phosphatases affect wall teichoic acid composition and phage resistance
Tyrosine phosphatase (PTP)-like proteins exist in many bacteria and are segregated into two major groups: low molecular weight and conventional. The latter group also has activity as phosphoinositide phosphatases. These two kinds of PTP are suggested to be involved in many aspects of bacterial physiology including stress response, DNA binding proteins, virulence, and capsule/cell wall production. By annotation, Listeria monocytogenes possesses two potential low molecular weight and two conventional PTPs. Using L. monocytogenes wild-type (WT) strain 10403S, we have created an in-frame deletion mutant lacking all four PTPs, as well as four additional complemented strains harboring each of the PTPs. No major physiological differences were observed between the WT and the mutant lacking all four PTPs. However, the deletion mutant strain was resistant to Listeria phages A511 and P35 and sensitive to other Listeria phages. This was attributed to reduced attachment to the cell wall. The mutant lacking all PTPs was found to lack N-acetylglucosamine in its wall teichoic acid. Phage sensitivity and attachment was rescued in a complemented strain harboring a low molecular weight PTP (LMRG1707
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