An alternative HER-2/neu transcript of 8 kb has an extended 3'UTR and displays increased stability in SKOV-3 ovarian carcinoma cells.
HER-2/neu is a potent oncogene that predicts poor outcome when overexpressed in ovarian cancer. The SKOV-3 ovarian carcinoma cell line, one of the only models for HER2-driven ovarian cancer, expresses a major uncharacterized 8-kb alternative HER-2 transcript.


OBJECTIVE
The aim of this study was to characterize the structure and determine the origin of the alternative sequence and examine the possible role of the 8-kb alternative transcript in overexpression of the HER-2 gene.


METHODS
The structure of the 8-kb transcript was investigated using polymerase chain reaction (PCR) and nucleotide sequencing of cDNA clones. PCR analysis of genomic DNA was used to assess the origin of the 8-kb transcript. The stability of the 8-kb mRNA was assessed by Northern blot analysis of RNA extracted from cells treated with transcriptional inhibitors.


RESULTS
Similar 5'UTR and coding sequence but an extended 3'UTR were contained in the 8-kb compared to the well-characterized 4.5-kb HER-2 transcript. Genomic DNA had continuity between the novel 3'UTR sequence from the 8-kb transcript and adjacent HER-2 terminal exon sequence. The 8-kb transcript had a half-life of 13 h compared to 5.5 h for the 4.5-kb transcript (P<0.01).


CONCLUSIONS
The 8-kb transcript is generated from alternative polyadenylation site usage rather than gene rearrangement. Since the 8-kb transcript contains alternative sequence found at the 3' end of the normal HER-2 gene, it could be expressed in other cells. Increased stability of the 8-kb transcript may confer a selective advantage for SKOV-3 cells by providing enhanced HER-2 expression.
Doherty
J K
JK
Department of Cell and Developmental Biology, Oregon Health Sciences University, Portland, Oregon 97201, USA.
Bond
C T
CT
Hua
W
W
Adelman
J P
JP
Clinton
G M
GM
D020413:3' Untranslated Regions / Q000235:genetics*; D020121:5' Untranslated Regions / Q000235:genetics*; D001483:Base Sequence; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics; D006801:Humans; D008969:Molecular Sequence Data; D010051:Ovarian Neoplasms / Q000235:genetics*; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics*; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured
D020413:3' Untranslated Regions; D020121:5' Untranslated Regions; D018719:Erb-b2 Receptor Tyrosine Kinases