Inhibition of DNA Synthesis and Mitosis by DNA Affinity Proteins Released from Thymus Cells during in Vitro Incubation

[摘要] References(28)During in vitro incubation of thymus cells, proteins with anaffinity for single stranded DNA (ss-DNA) are released into the medium. In competitive experiments with unlabeled DNA, the ss-DNA-binding proteins showed a high specificity toward ss-DNA. However, they did not recognize the difference between heterologous and homologous ss-DNA. Thymus cells were incubated in MEM for 3 h at 37°C. The ss-DNA-binding proteins in the cell culture medium then were purified by ss-DNA-cellulose chromatography. The effect of the ss-DNA-binding proteins on lymphocytes or nonlymphocytes was studied in vitro by the incorporation of [3H]-thymidine. The addition of ss-DNA binding proteins to the assay system markedly inhibited the DNA, synthesis of nonactivated spleen cells. Spleen cells activated with phytohemagglutinin also were inhibited by the addition of ss-DNA-binding proteins. Further experiments showed that the DNA-binding proteins inhibited the DNA-synthesis of L-cells ; this activity was heat labile. The proteins also inhi-bited the mitosis of L-cells.

[学科分类] 分子生物学，细胞生物学和基因