Figure 3

HRAS over-expression causes isoform specific regulation of Epidermal Growth Factor Receptor (EGFR) in human mammary epithelial cells. (A) Probesets on the Affymetrix U133 2.0 plus array interrogate EGFR expression at seven different genomic locations. Up and down arrows indicate each probeset's expression changes in HRAS over-expression compared to GFP controls. Probeset 5 experienced a significant decrease in expression with HRAS over-expression, but was not expressed above background. B) UCSC genomic alignment of probesets and EGFR isoforms. Four previously observed EGFR isoforms (A, B, C and D) are shown with exons represented as black boxes and introns as hashed lines. Extracellular, transmembrane, and intracellular domain regions are shown below the alignment. C-F) Scatter plots of logged expression levels of all 55 samples (GFP, MYC, SRC, CTNNB1, E2F3, and HRAS) for selected pairs of probesets C) Probesets 1 and 2 target a transcript region common to all major isoforms and exhibit highly correlated expression (R2 = .95). D) Probesets 1 and 3 target the common region vs. isoform B specific region and demonstrate a weak inverse relationship (R2 = .36). E) Probesets 1 and 6 interrogate the common vs. AShort isoform region, demonstrating a high degree of correlation across all samples (R2 = .87). F) In contrast, probesets 1 and 7 interrogate common and ALong isoform region and are not correlated (R2 = .01) due to the HRAS induced 3'UTR shortening of EGFR A transcripts.