An inducible gene involved in commitment of lymphocytes to transform

Abstract

CONCANAVALIN A (Con A) stimulates nondividing lymphocytes (in G₀) to transform and enter the division cycle¹. Within 3 h a significant proportion of the cells become committed to transform and do so after the removal of Con A (ref. 2). When the translation of mRNA into protein is inhibited (by low concentrations of anisomycin) lymphocyte transformation is also blocked³. Anisomycin has proved particularly useful in studying lymphocyte transformation because its effect is reversible: in the presence of Con A it holds the cells in G₀, apparently without adverse effects, and the cells transform following its removal³. Using anisomycin it has been shown that Con A induces the synthesis of factor(s) which commit lymphocytes to transform³. I have examined the stability and nature of the ‘transformation signal’, again exploiting the reversible effect of anisomycin, and report here that on binding to the surface of nondividing lymphocytes, Con A induces the transcription of a short-lived mRNA. This mRNA encodes a ‘transformation factor’ which, when translated, commits lymphocytes to enter the division cycle; extracellular Con A is no longer required.