Public Health Research Institute

About: Public Health Research Institute is a based out in . It is known for research contribution in the topics: Population & Randomized controlled trial. The organization has 4889 authors who have published 8149 publications receiving 276945 citations.

The phage N4 virion RNA polymerase catalytic domain is related to single-subunit RNA polymerases.

Abstract: In vitro, bacteriophage N4 virion RNA polymerase (vRNAP) recognizes in vivo sites of transcription initiation on single-stranded templates. N4 vRNAP promoters are comprised of a hairpin structure and conserved sequences. Here, we show that vRNAP consists of a single 3500 amino acid polypeptide, and we define and characterize a transcriptionally active 1106 amino acid domain (mini-vRNAP). Biochemical and genetic characterization of this domain indicates that, despite its peculiar promoter specificity and lack of extensive sequence similarity to other DNA-dependent RNA polymerases, mini-vRNAP is related to the family of T7-like RNA polymerases.

Growth stage signal transduction and the requirements for srfA induction in development of competence.

Abstract: srfA is an operon needed for the development of genetic competence in Bacillus subtilis. This operon is normally expressed at a low level during growth, and its transcription increases sharply just before the transition to stationary phase. The genetic requirements for the full expression of srfA were previously examined in several laboratories and shown to include spo0A, spo0H, spo0K, comQ, and comA. In the present study these results were confirmed with an isogenic set of strains. We have also shown that comP is needed for srfA expression but that other regulatory genes required for competence (degU, sin, and abrB) are not needed for the expression of srfA. We have used the expression of srfA under control of the regulatable Pspac promoter to study the kinetics of competence development and to determine whether the genes ordinarily required for expression of srfA are needed for any additional roles during the development of competence. When expression of srfA was driven from Pspac, competence was expressed constitutively throughout growth. Furthermore, when srfA was expressed from Pspac, the spo0K, comQ, comP, and comA determinants were no longer required for the expression of competence. We conclude therefore that the multiple signals which trigger the initiation of competence development in relation to growth stage are ordinarily received prior to the increase in srfA expression. We propose that these signals are mediated by the products of spo0K, comQ, comP, and comA, resulting in the phosphorylation of ComA by ComP. This in turn would enable ComA to function as a positive transcription factor for srfA, leading to the elaboration of the srfA product(s) and the consequent initiation of competence. We also propose that this is the major, and possibly the only, role for the spo0K, comQ, comP, and comA products during competence development.

Neisseria gonorrhoeae Kills Carcinoembryonic Antigen-Related Cellular Adhesion Molecule 1 (CD66a)-Expressing Human B Cells and Inhibits Antibody Production

Abstract: Neisseria gonorrhoeae cells (gonococci [GC]), the etiological agents for gonorrhea, can cause repeated infections. During and after gonococcal infection, local and systemic antigonococcal antibody levels are low. These clinical data indicate the possibility that GC may suppress immune responses during infection. Carcinoembryonic antigen-related cellular adhesion molecule 1 (CEACAM1 or CD66a), a receptor for GC opacity (Opa) proteins, was shown to mediate inhibitory signals. In the present study, human B cells were activated by interleukin-2 to express CEACAM1 and then stimulated to secrete antibodies and simultaneously coincubated with Opa − and OpaI GC of strain MS11. Our results show that this OpaI GC has the ability to inhibit antibody production. The interaction of GC and CEACAM1 with human peripheral B cells also results in induction of cell death. The same findings were observed in DT40 B cells. This CEACAM1-promoted cell death pathway does not involve the inhibitory signals or the tyrosine phosphatases SHP-1 and SHP-2 but depends on Bruton9s tyrosine kinase in DT40 cells. Our results suggest that Neisseria gonorrhoeae possesses the ability to suppress antibody production by killing CEACAM1-expressing B cells.

Tn554—a site-specific represser-controlled transposon in Staphylococcus aureus

Abstract: PREVIOUS studies have defined a specific element in Staphylococcus aureus containing determinants of inducible erythromycin resistance and spectinomycin resistance. This element has many plasmid-like properties1,2 but is not associated with detectable extra-chromosomal DNA2. The resistances are similar in mechanism to those ordinarily associated with plasmids3,4 (J. Davies, personal communication); the element can be transferred by transduction2 or transformation to a rec− recipient with the same efficiency as to a rec+, and the two determinants show essentially 100% linkage in genetic transfer. Consequently, this linkage group has previously been referred to as a ‘pseudoplasmid’ (ref. 2). On the basis of the results presented here, we suggest that this pseudoplasmid is actually the prototype of a new class of transposon, which functions by means of a highly efficient, represser-controlled, site-specific integration–excision mechanism. This transposon, designated Tn554 (EmSp), can be most easily envisaged as a prophage-like element that lacks replicative autonomy and other vegetative phage functions.