‘Pleiotypic’ and ‘Specific’ Hormonal Control of Gene Expression in Mammalian Cells

Abstract

I should like to propose that regulation by a variety of hormones and other growth-stimulating substances is effected in two ways, which I shall refer to as the ‘pleiotypic’ [1] and ‘specific’ modes of regulation. The pleiotypic control system refers to a coordinated set of reactions which respond in a characteristic way when cellular growth is stimulated by a specific hormone. Some of the reactions under this type of general control are:

• (1) the uptake of glucose and of various precursors for macromolecular synthesis;

• (2) RNA synthesis, particularly of ribosomal and transfer RNA;

• (3) protein synthesis and the state of polysome assembly (probably determined by the initiation reaction);

• (4) the degradation of intracellular proteins and other macromolecules.

Responses in all of the above reactions follow the administration of the steroid hormones, thyroxin, insulin and growth hormone to animals (see [1] for references); similar reactions are regulated when lymphocytes are stimulated by phytohemagglutinin, erythroid cells by erythropoietin, and in other conditions where the growth of certain cells is stimulated by a specific humoral agent. Table 1 lists some of the reaction under pleiotypic control and how they are regulated in specific situations.