title: In vitro transcription of the c-myc first exon may be influenced by the extent of chromatin assembly.
abstract: The first exon of the human c-myc gene can be transcribed by either RNA polymerase II or RNA polymerase III. The molecular factors contributing to polymerase selection are not yet completely defined. We have examined the role of chromatin structure in regulating transcription by RNA polymerase III. Using as competitor a pol III gene in both a cis and trans arrangement, we demonstrate that c-myc gene expression is facilitated from templates containing a minimal number of fully assembled nucleosomes. The removal of excess histones by DNA titration leads to an elevated level of c-myc expression. These results suggest that either the c-myc expression is inhibited when the template is fully packaged into chromatin or that the affinity of RNA polymerase for the regulatory elements of this exon is such that a template, devoid of histones, is required for transcriptional initiation.
authors.affiliation: Jefferson Cancer Institute, Thomas Jefferson School of Medicine, Philadelphia, Pennsylvania 19107.
authors.forename: T P
authors.initials: TP
authors.lastname: Nguyen
authors.forename: E B
authors.initials: EB
authors.lastname: Kmiec
mesh_terms: D000818:Animals; D002474:Cell-Free System; D002843:Chromatin / Q000737:chemistry*; D004247:DNA; D005091:Exons; D016259:Genes, myc; D006801:Humans; D011487:Protein Conformation; D012319:RNA Polymerase II / Q000378:metabolism; D012320:RNA Polymerase III / Q000378:metabolism; D012343:RNA, Transfer / Q000235:genetics; D013698:Templates, Genetic; D014158:Transcription, Genetic; D014982:Xenopus laevis
chemical_list: D002843:Chromatin; D004247:DNA; D012343:RNA, Transfer; D012319:RNA Polymerase II; D012320:RNA Polymerase III