Interactions between upstream and core promoter sequences determine gene expression and nucleosome positioning in tobacco PR-1a promoter

Niraj Lodhi, Amol Ranjan, Mala Singh, Rakesh Srivastava, Sudhir Pratap Singh, Chandra Prakash Chaturvedi, Suraiya Anjum Ansari, Samir V. Sawant, Rakesh Tuli

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)

Abstract

The expression of PR-1a gene in tobacco is accompanied by changes in the chromatin architecture over its promoter region. The transcription initiates when the gene is induced in defense response, a condition that can be simulated experimentally by external application of salicylic acid. Mutagenesis of the core promoter sequence established that the TATA-box was critical to the expression of PR-1a gene. In order to study functional specificity between the core promoter and upstream activator region, the native core promoter was exchanged with that of a heterologous salicylic acid inducible promoter, Pcec. The core promoter and the activator region of PR-1a together determine its tightly regulated expression, slow kinetics of induction by SA and several fold induction of expression. In uninduced state, a single nucleosome was present over the core promoter of PR-1a. It masked both the TATA-box and the transcription initiation region. The transcriptional activation of the promoter by SA was accompanied by shift in the position of this nucleosome. The chimeric promoters failed to show inducibility or gave very low level of induction. They showed failure in shifting the nucleosome from the core promoter region. The promoter Pcec expressed constitutively at a high uninduced level in spite of a nucleosome over the TATA-box region. However, in this case, the nucleosome did not mask the transcript initiation region. The TATA-box nucleosome was shifted as the expression increased further, following induction by SA. A fully induced Pcec had the TATA-box fully exposed, though a weak nucleosome appeared on the + 1 region. The results support a close relationship among promoter sequence architecture, nucleosome positioning and PR-1a expression.

Original languageEnglish
Pages (from-to)634-644
Number of pages11
JournalBiochimica et Biophysica Acta - Gene Regulatory Mechanisms
Volume1779
Issue number10
DOIs
Publication statusPublished - Oct 2008
Externally publishedYes

Keywords

  • Chimeric promoter
  • Gene expression
  • Histone modification
  • Initiator
  • TATA-box

ASJC Scopus subject areas

  • Biophysics
  • Structural Biology
  • Biochemistry
  • Molecular Biology
  • Genetics

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