Purchase this article with an account.
Zhe Jing, Suraj P. Bhat; A Positional and Orientation Specific Sequence Controls Expression from the Heat Shock Promoter of αB-crystallin. Invest. Ophthalmol. Vis. Sci. 2011;52(14):24.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
The identification of the information content of eukaryotic promoters has remained confined to universal landmarks and conserved sequence elements such as enhancers and transcription factor binding motifs. Because directionality is innate to the genetic code and its reading, it is reasonable to postulate that in its simplest form, the control of the decoding process (transcription) may also depend on gene-specific elements which, unlike enhancers and transcription factor (TF) binding sites, may have strict positional and orientation constraints to ensure relevant control. Here we present data on the existence of such a sequence in the promoter of the eukaryotic small heat shock protein gene, αB-crystallin (αB).
Gel-shift analyses were performed to ascertain the import of the sequences in the heat shock promoter. In vivo significance of various sequences was investigated with assessing the expression of the reporter in human adult retinal pigment epithelial cell line 19 (ARPE19). This cell line expresses appreciable amount of αB-crystallin.
Gel-shift analyses indicated that 5’ sequences surrounding the heat shock element (HSE) were essential for efficient binding of HSF4 to HSE in vitro. We studied the functional consequences of manipulating these sequences in vivo in human retinal pigment epithelial cells. We demonstrate that expression from this promoter is dependent on the integrity of a 10 bp DNA sequence adjoining the HSE on the 5’ end. This sequence element works only in appropriate position and orientation. When moved more than one nucleosome length of DNA (-154 bp) away from the transcription start site it impacts expression drastically suggesting its involvement in local promoter access. Importantly, the promoter is active, albeit inefficiently in the absence of HSE, but it doesn’t work without the 10 bp sequence indicating that the presence of transcription factors and enhancers alone is not sufficient for expression.
These data point to existence of gene-specific, linear positional information elements (PIEs) that may be crucial in allowing activation of a gene even in the presence of activation signals, be they cis- or transacting factors.
This PDF is available to Subscribers Only