Open AccessDNase I-resistant nontranscribed spacer segments of mouse ribosomal DNA contain poly(dG-dT).poly(dA-dC).
Author(s) -
J. R. Thomas,
R. I. Bolla,
J S Rumbyrt,
David Schlessinger
Publication year - 1985
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.82.22.7595
Subject(s) - biology , nucleolus , spacer dna , transcription (linguistics) , dna , dnase i hypersensitive site , microbiology and biotechnology , deoxyribonuclease i , ribosomal dna , enhancer , coding region , ribosomal rna , genetics , gene , internal transcribed spacer , transcription factor , base sequence , phylogenetics , linguistics , philosophy , cytoplasm
The nontranscribed spacer regions (NTS) that adjoin the coding portion of mouse ribosomal DNA are protected in nucleoli against exhaustive DNase I digestion. Since these sequences are degraded by the enzyme after they are extracted by phenol, the protection is suggested to result from the binding of specific proteins. The nucleolar structure would thus be organized to protect NTS sequences and expose the coding sequences for transcription. We show here that these protected sequences include tracts of poly(dG-dT).poly(dA-dC). We also report that these sequences are localized in regions flanking the rRNA transcription unit. These sequences can potentially form Z-DNA. The organized DNase I-resistant NTS structure in which they participate could be involved in structuring the nucleolus or in regulating transcription because poly(dG-dT).poly(dA-dC) sequences and portions of spacer rDNA can serve as transcriptional enhancer elements.