title: Relative base composition of initiation sites for transcription in developing frog embryos.
abstract: The use of an inhibitor (0.4 N (NH4)2SO4) and an activator (sodium polydextran sulfate) of initiation of transcription in nuclei of frog embryos in vitro indicated that initiation sites for transcription are relatively A--T-rich. Comparison of incorporation of labeled ATP, UTP, and GTP, when initiation of transcription is prevented, indicates that initiation sites become relatively less A--T-rich as development proceeds. Inhibition of initiation of transcription in isolated nuclei blocks the normal increase in rate of transcription that occurs when cells enter the S phase, showing that an increased level of transcription depends upon a greater number of initiation sites.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001482:Base Composition; D046508:Culture Techniques; D004247:DNA / Q000032:analysis*; D006151:Guanosine / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D007399:Interphase; D007700:Kinetics; D012332:RNA, Heterogeneous Nuclear / Q000096:biosynthesis*; D011894:Rana pipiens / Q000196:embryology; D012293:Rifampin / Q000494:pharmacology; D014158:Transcription, Genetic; D014529:Uridine / Q000378:metabolism; D014544:Uridine Triphosphate / Q000378:metabolism
chemical_list: D012332:RNA, Heterogeneous Nuclear; D006151:Guanosine; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D004247:DNA; D014544:Uridine Triphosphate; D012293:Rifampin; D014529:Uridine