title: The Myb domain of the largest subunit of SNAPc adopts different architectural configurations on U1 and U6 snRNA gene promoter sequences.
abstract: The small nuclear RNA (snRNA) activating protein complex (SNAPc) is essential for transcription of genes that encode the snRNAs. Drosophila melanogaster SNAPc (DmSNAPc) consists of three subunits (DmSNAP190, DmSNAP50 and DmSNAP43) that form a stable complex that recognizes an snRNA gene promoter element called the PSEA. Although all three subunits are required for sequence-specific DNA binding activity, only DmSNAP190 possesses a canonical DNA binding domain consisting of 4.5 tandem Myb repeats homologous to the Myb repeats in the DNA binding domain of the Myb oncoprotein. In this study, we use site-specific protein-DNA photo-cross-linking technology followed by site-specific protein cleavage to map domains of DmSNAP190 that interact with specific phosphate positions in the U6 PSEA. The results indicate that at least two DmSNAP190 Myb repeats contact the DNA in a significantly different manner when DmSNAPc binds to a U6 PSEA versus a U1 PSEA, even though the two PSEA sequences differ at only 5 of 21 nucleotide positions. The results are consistent with a model in which the specific DNA sequences of the U1 and U6 PSEAs differentially alter the conformation of DmSNAPc, leading to the subsequent recruitment of different RNA polymerases to the U1 and U6 gene promoters.
authors.affiliation: Department of Chemistry and Biochemistry, Molecular Biology Institute, San Diego State University, San Diego, CA 92182-1030, USA.
authors.forename: Yoon Soon
authors.initials: YS
authors.lastname: Kang
authors.affiliation: Department of Biology, Molecular Biology Institute, San Diego State University, San Diego, CA 92182-1030, USA.
authors.forename: Michelle
authors.initials: M
authors.lastname: Kurano
authors.affiliation: Department of Chemistry and Biochemistry, Molecular Biology Institute, San Diego State University, San Diego, CA 92182-1030, USA wstumph@mail.sdsu.edu.
authors.forename: William E
authors.initials: WE
authors.lastname: Stumph
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000737:chemistry; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism*; D029721:Drosophila Proteins / Q000737:chemistry* / Q000378:metabolism*; D008957:Models, Genetic; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012342:RNA, Small Nuclear / Q000235:genetics*
chemical_list: D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; C534010:Pbp95 protein, Drosophila; D012342:RNA, Small Nuclear; C405483:U1 small nuclear RNA; C405486:U6 small nuclear RNA; D004247:DNA