The main contents of this chapter include all of the following: Categories of activators, structures of the DNA-Binding motifs of activators, independence of the domains of activators, functions of activators, interaction among activators, regulation of transcription factors. | Molecular Biology Fifth Edition Chapter 12 Transcription Activators in Eukaryotes Lecture PowerPoint to accompany Robert F. Weaver Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Transcription Activators of Eukaryotes The general transcription factors by themselves dictate the starting point and direction of transcription but they are capable of sponsoring only a low level of transcription or basal transcription Transcription of active genes in cells rises above the basal level Eukaryotic cells have additional, gene-specific transcription factors called activators that bind to DNA elements called enhancers to provide the extra needed boost to transcription 12- Categories of Activators Activators can stimulate or inhibit transcription by RNA polymerase II Structure is composed of at least 2 functional domains DNA-binding domain Transcription-activation domain Many also have a dimerization domain 12- DNA-Binding Domains Protein . | Molecular Biology Fifth Edition Chapter 12 Transcription Activators in Eukaryotes Lecture PowerPoint to accompany Robert F. Weaver Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Transcription Activators of Eukaryotes The general transcription factors by themselves dictate the starting point and direction of transcription but they are capable of sponsoring only a low level of transcription or basal transcription Transcription of active genes in cells rises above the basal level Eukaryotic cells have additional, gene-specific transcription factors called activators that bind to DNA elements called enhancers to provide the extra needed boost to transcription 12- Categories of Activators Activators can stimulate or inhibit transcription by RNA polymerase II Structure is composed of at least 2 functional domains DNA-binding domain Transcription-activation domain Many also have a dimerization domain 12- DNA-Binding Domains Protein domain is an independently folded region of a protein DNA-binding domains have DNA-binding motif Part of the domain having characteristic shape specialized for specific DNA binding Most DNA-binding motifs fall into 3 classes; zinc-containing modules, homeodomains and bZIP and bHLH motifs 12- Zinc-Containing Modules There are at least 3 kinds of zinc-containing modules that act as DNA-binding motifs All use one or more zinc ions to create a shape to fit an a-helix of the motif into the DNA major groove Zinc fingers Zinc modules Modules containing 2 zinc and 6 cysteines 12- Homeodomains These domains contain about 60 amino acids Resemble the helix-turn-helix proteins in structure and function Found in a variety of activators Originally identified in homeobox proteins regulating fruit fly development 12- bZIP and bHLH Motifs A number of transcription factors have a highly basic DNA-binding motif linked to protein dimerization motifs Leucine zippers Helix-loop-helix Examples .
