Geneviève Lemaire

Autogenous translational repression of bacteriophage T4 gene 32 expression in vitro

The protein product of the bacteriophage T4 gene 32 is a single-stranded DNA binding protein which functions during phage DNA repair, replication and recombination. Recently the gene 32 protein was shown to participate in the regulation of its own expression. Although the purified protein is known to interact with DNA, the autoregulation was shown to occur at the translational level. The previous analysis in vivo, although coherent, was indirect. We report here direct cell-free experiments in which purified gene 32 protein specifically represses translation of gene 32 messenger RNA.

Low response of BALB/c macrophages to priming and activating signals.

Trehalose dimycolate (TDM), a mycobacterial glycolipid, is a powerful macrophage‐priming agent. However, its efficiency seems limited in the case of BALB/c mice. Peritoneal macrophages harvested from TDM‐treated BALB/c mice did not control BCG growth in vitro as efficiently as similar macrophages from two other mouse strains, (B6 × D2)F1 and C57BL/6, which are respectively Bcg r and Bcg s. BALB/c macrophages elicited by TDM also exhibited a low capacity to produce hydrogen peroxide and, after activation by lipopolysaccharide (LPS), weak cytostatic activity against P815 mastocytoma cells. Finally, alkaline phosphodiesterase, a marker of resident and inflammatory macrophages, was still expressed at a high level in macrophages of BALB/c mice treated with TDM. Low responsiveness of BALB/c macrophages to stimuli was not observed with TDM only; activation for tumor cytotoxicity of thioglycolateelicited macrophages from BALB/c mice required also higher doses of interferon‐γ, and LPS. l‐Arginine–dependent production of nitric oxide was inducible in macrophages from BALB/c mice, but the conditions required for its induction were more stringent. Thus, the reduced antiproliferative effects of BALB/c macrophages may be due to uncomplete induction of NO synthase after suboptimal stimulation.

Interaction entre la tryptophane-τRNA synthétase et le tryptophane ou certains analogues du tryptophane

Abstract Beef pancreatic tryptophan-sRNA synthetase ( l -tryptophan:sRNA ligase (AMP), EC 6.1.1.2) is protected against heat denaturation by l -tryptophan and against ϱ-chloromercuribenzoate or proteolytic inactivation by l - tryptophan + ATP . 25 tryptophan analogues were tested. None is as effective as l -tryptophan except l -tryptophan hydroxamate. The other amino acids and ATP alone are totally ineffective. A weak protection is afforded by tryptamine and this protection is enhanced by ATP, though ATP has no action of its own and does not bind covalently to tryptamine.

Cytostatic product(s) released by activated macrophages, unrelated to interleukin 1, tumor necrosis factor α, and interferon-αβ

Abstract Murine peritoneal macrophages activated for cytotoxicity by trehalose dimycolate in vivo and lipopolysaccharide in vitro released cytostatic factor(s) against EMT6 target cells, in 8-hr conditioned medium (CM). The cytostatic factor(s) completely blocked DNA synthesis by EMT6 cells within 16 hr. Other cell lines are less sensitive (P815 and R-L929) or resistant (KB and HT29) to the cytostatic effect of CM. The anti-proliferative activity of CM had a MW >10,000 Da, as judged by ultrafiltration. It was destroyed by proteases and strongly inhibited by P815 cell product(s). Conditioned media from nonactivated macrophages were not cytostatic against EMT6 cells. No relationship was found between cytostatic factor(s) in CM and interleukin 1 (IL-1), tumor necrosis factor α (TNF-α), and interferon- α β (IFN- α β ): the growth of EMT6 cells was unaffected by Hu.r.IL-1s and Hu.r.TNF-α and was only slightly inhibited by IFN- α β . Furthermore, cytostatic CM contained low levels of TNF and IFN activities. Finally, antibodies raised against murine IFN- α β had no effect on the cytostatic activity of CM.