Michiko Saito

Revised sequence of the nusA gene of Escherichia coli and identification of nusA11 (ts) and nusA1 mutations which cause changes in a hydrophobic amino acid cluster.

SummaryThe mutant nusA DNAs (nusA11 and nusA1) were sequenced. Single base substitutions caused by these mutations were found in the coding region of nusA. The nusA11 mutation, which is conditionally lethal, substituted Thr for the 181st Ala. Also, nusA1, which restricts λ growth, substituted Ala for the 183rd Ser. These two positions were located in the same hydrophobic amino acid cluster. This cluster seemed to be an essential region in the functional domain of NusA. In the course of these experiments, several mistakes in the published nusA nucleotide sequence were found. These errors are revised in this article. The molecular weight of NusA is accordingly revised to 54,430.

Effect of retinoic acid and 12-O-tetradecanoyl phorbol-13-acetate on the binding of epidermal growth factor to its cellular receptors

Binding of 125I-labelled epidermal growth factor (EGF) to C3H/2K cells and the effect of a tumor promotor, 12-O-tetradecanoyl phorbol-13-acetate (TPA) and of a tumor promotor antagonist, retinoic acid, on the binding was studied. Scatchard plot analysis of the binding showed the presence of two types of binding sites with different affinity to EGF. Treatment of the cells with retinoic acid for 1 h resulted in elevation of the affinity of both sites without changing their number per cell. Prolonged exposure to retinoic acid abrogated this elevation of the affinity and caused cycloheximide-sensitive increase of the number of the binding sites of both types. TPA inhibited binding of EGF to the cells by abolishing the binding to the high affinity sites, whereas retinoic acid, in the presence of TPA, enhanced it by increasing the number of the low affinity sites.

Agglutination of murine tumor cells by sera from various cancer patients

Sera from 72 of 94 patients with various malignancies and those from seven of nine pregnant womens agglutinated mouse ascitic tumor cells in vitro. Sera from 15 of 17 benign disease controls also agglutinated the cells, but none of the sera from 21 normal controls did. The agglutination activity of the sera from cancer patients was studied in detail. The activity, which remained after absorption with liver tissue from normal adult mice and also with blood group A substance, was absorbed completely by embryonic tissue of the mouse and partially by perchloric acid soluble fraction (PCAS) of the target cells or by carcinoembryonic antigen (CEA) from human cancer, and therefore was related to cross‐reacting tumor‐associated embryonic materials. The agglutination was inhibited by monosaccharides such as galactose or N‐acetyl glucosamine. The receptor activity of PCAS for the agglutination factors in the sera from cancer patients was also affected by treatment with glycosidases, but not by trypsinization. These results indicated that carbohydrate moieties of the cell surface components were involved in the agglutination. It was thus evident that a sort of humoral reaction took place in cancer patients against tumor‐associated embryonic materials on the tumor cell surface, that a considerable part, at least, of such reactions were directed to their carbohydrate moieties and that their teminal sugar residues played the most important role in the reaction. The humoral factors induced by this reaction was located in β‐globulin fraction of the serum protein. The extent of such humoral reaction by the hosts was semiquantitated by the simple in vitro agglutination method. Cancer 40:693–699, 1977.

Agglutination of murine tumor cells by sera from patients with autoimmune diseases.

A method of in vitro agglutination of murine ascitic tumor cells which had been used to detect and to semiquantitate components with saccharide-binding properties in sera from cance