Activation of p34cdc2 protein kinase by microinjection of human cdc25C into mammalian cells. Requirement for prior phosphorylation of cdc25C by p34cdc2 on sites phosphorylated at mitosis.

International audienceHuman cdc25C protein, a specific tyrosine phosphatase that activates the p34cdc2 protein kinase at mitosis, is itself a phosphoprotein that shows increased phosphorylation during the G2-M transition. In vitro, cdc25C protein is substantially phosphorylated by purified p34cdc2-cyclin B protein kinase. Of seven putative phosphorylation sites for p34cdc2 protein kinase present in human cdc25C, five are phosphorylated by p34cdc2 protein kinase in vitro, as assessed by tryptic phosphopeptide mapping and peptide sequencing. These same sites are also phosphorylated in vivo during the G2-M transition in normal mammalian fibroblasts and have been precisely mapped. The cdc25C phosphorylated in vitro by p34cdc2 protein kinase exhibits a 2-3-fold higher activity than the nonphosphorylated cdc25C, as assayed by activation of inactive cdc2 prokinase. Microinjection of purified cdc25C proteins into living fibroblasts reveals that only the phosphorylated form of cdc25 is highly effective in activating G2 cells into premature prophase in a manner similar to microinjection of purified active p34cdc2 protein kinase. Together these data show that multisite phosphorylation of cdc25C by p34cdc2-cyclin B protein kinase occurs at the G2-M transition and is sufficient to induce the autoamplification of cdc2/M-phase promoting factor necessary to drive somatic mammalian cells into mitosis

[Clinical assessment of the risk of Human Immunodeficiency virus (HIV) infection in the population consulting an anonymous and free screening center].

INTRODUCTION: The anonymous and free AIDS screening centers were developed in France in 1987 to incite the general population to undergo screening for HIV infection. The aim of this paper was to conduct a prospective study describing the principle characteristics and level of risk of those consulting a center in the Year 1999. POPULATION AND METHODS: A face to face physician-consultant questionnaire was proposed to all the consultants that Year. It included 20 questions regrouped in general characteristics of the subject, number of previous screenings, reason for screening, type of risk taken, date of last risk taken, and number of sexual partners during the past 12 Months and throughout their life without the use of a condom. RESULTS: Two thousand six hundred seventy-eight persons consulted (sex ratio=1) aged a mean of 25.8 Years. The men were older than the women (respectively 27 versus 24.6; p<0.05). The reason for screening was a decision made by the couple in 44.6 p. 100, an unprotected sexual relationship in 47.6 p. 100 another reason in 7.6 p. 100 and drug abuse in 0.2 p. 100 of cases. The sex mode declared was heterosexual in 94.5 p. 100 and homo or bisexual in 5.4 p. 100. The majority of those consulting (66.2 p. 100) had had between 0 and 2 partners during the past 12 Months; 66 p. 100 had had more than 10 during their life without using a condom. The assessment of the global risk by the physician was: very high in 1 p. 100, high in 2.5 p. 100, moderate in 13.3 p. 100, low in 70.7 p. 100 and nil in 12.5 p. cent. Five HIV infections were diagnosed, all in persons at high or very high risk. DISCUSSION: These results should stimulate the radical differentiation of the management of persons consulting according to the level of risk identified by the medical questionnaire