Sinorhizobium meliloti plasmid pRm1132f replicates by a rolling-circle mechanism.

pRm1132f isolated from Sinorhizobium meliloti is a group III rolling-circle-replicating (RCR) plasmid. At least seven of eight open reading frames in the nucleotide sequence represented coding regions. The minimal replicon contained a rep gene and single- and double-stranded origins of replication. Detection of single-stranded plasmid DNA confirmed that pRm1132f replicated via an RCR mechanism.

Down-regulation of interleukin-1beta production and PGE2 accumulation by an indomethacin-phenylalanine derivative in human monocytes.

This study was initiated to investigate the mechanism of action of a new indomethacin derivative, indomethacin-phenylalanine (indo-Phe) in human monocytes. We determined the effect of indo-Phe on the induction by LPS of prostaglandin-E2 (PGE2) and interleukin-1beta (IL-1beta) production in human monocytes. Indomethacin and indo-Phe inhibited the PGE2 synthesis in treated and untreated IL-1beta or LPS-treated monocytes. Furthermore, in IL-1beta and LPS-treated monocytes, prostaglandin G/H synthase-1 (PGHS-1) protein expression was down-regulated with indomethacin or its indo-Phe analog whereas the level of the inducible protein (PGHS-2) was up-regulated. We analyzed the effect of indomethacin and indo-Phe on the expression of IL-1beta protein in LPS-treated monocytes and found that indo-Phe blocked the LPS-induction of IL-1beta synthesis while indomethacin did not. These differential effects of indomethacin and indo-Phe suggest that two independent ways are involved in the stimulation of monocytes by LPS: the PGHS-2 protein induction and the IL-1beta secretion.

Effect of an aryl chloroethyl urea on tubulin and vimentin syntheses in a human breast cancer cell line.

A new class of antineoplastic agents, 1-aryl-3-(2-chloroethyl) ureas (CEUs), was recently developed in our laboratory. To optimize the pharmacological and the biological properties of this new class of compounds and to determine its mechanism of action, at the cellular level, we studied the effect of 4-tert-butyl-[3-(2-chloroethyl) ureido] benzene (tBCEU) on MDA-MB-231, a human breast cancer hormone-independent cell line. The effect of tBCEU on protein synthesis and on the accumulation of specific mRNAs was evaluated. The results indicate that tBCEU increases the synthesis of at least two proteins present in the cytoskeleton: tubulin and vimentin. The effect of tBCEU on their transcripts indicates that tBCEU decreases the accumulation of tubulin and vimentin mRNA. These results suggest that the antineoplastic activity of tBCEU is in part related to an alteration in the synthesis pathway of tubulin and vimentin.

DNA methylation in Neisseria gonorrhoeae and other Neisseriae.

It has been reported in the literature that Neisseria gonorrhoeae DNA is modified by the methyltransferases (MTases) M.NgoI, M.NgoII, and M.NgoIII, as well as three other cytosine MTases and one adenine MTase, even if the corresponding restriction endonucleases are not present. We envisioned the possibility of cloning one of the N. gonorrhoeae MTase-encoding genes for use as a species-specific DNA probe. We therefore undertook a survey of methylation patterns of several clinical isolates of N. gonorrhoeae and N. meningitidis as well as ATCC strains of other Neisseriae. We found, from digestion patterns with isoschizomers, one N. gonorrhoeae strain that lacked M.NgoII and two that lacked M.NgoIII. All N. meningitidis strains (save one) were resistant to digestion with NlaIV thus possessing an MTase like NgoV, and one was resistant to SstII, thus having an NgoIII-like MTase. None were resistant to isoschizomers of NgoI, NgoIII and NgoIV. Some other Neisseriae had an MTase with NlaIV (NgoV) specificity, but none had NgoI, II, III or IV specificity, except for the Branhamella-like N. caviae-ovis group and N. lactamica where these specificities were present in at least one strain of this group. Therefore, among the Neisseriae other than N. caviae only M.NgoI is N. gonorrhoeae-specific.