RNA Polymerases and Controlling Factors from Plant Cell Nuclei

Abstract

Transcriptional regulation in higher organisms occurs by activation or inactivation of entire chromosomes, large chromosomal segments, and possibly smaller units. The phenomenon of puffing (1), where fairly large sections of chromosomes are activated together, may indicate the expression of the functionally related clusters. That such clusters of genes actually occur in higher organisms has been shown (2). Crick’s (3) hypothesis that the function of most of the DNA is to regulate the activity of the rest of the DNA seems to originate from several lines of evidences. Britten and Davidson (4) suggested that the control is exerted by the extra DNA carried by higher organisms, especially by the repetitive DNA, and they pointed out the necessity of a sensor gene and integrator genes besides the regulator and structural genes. Georgiev et al. (5) have recently invoked similar types of multielemental control systems in eukaryotes. Thus inasmuch as different investigators have hypothesized a number of regulatory elements, regulation of the transcription process in the eukaryotes must be studied in detail.