Identification of an alternatively spliced RNA for the Ras suppressor RSU-1 in human gliomas.
Previous studies demonstrated that the Ras suppressor, RSU-1, localizes to human chromosome 10p13, a region frequently deleted in high grade gliomas, and that RSU-1 expression inhibited the tumorigenesis of a glioblastoma cell line. We have now examined RNA from human glial tumors for RSU-1 expression by RT-PCR using primers for the 5' and 3' ends of the RSU-1 open reading frame. Analysis of the amplified RSU-1 cDNA demonstrated that in addition to the entire 858 bp RSU-1 open reading frame, a shorter 725 bp RSU-1 fragment was amplified as well. Sequencing of this product revealed that it encoded a RSU-1 cDNA product which was missing a single 133 bp internal exon. This exon-deleted product was found in 30% of the high grade gliomas studied and 2/3 oligodendrogliomas, but not in other CNS tumors, bladder or colon tumors or normal tissue. The exon-deleted RSU-1 product was infrequently detected in RNA from human tumor cell lines. Expression of an HA-tagged form of the deleted RSU-1 protein in transfected Cos 1 cells revealed that the protein was unstable, with a half life of less than 1 h, in contrast to the full length HA-tagged Rsu-1 protein which was stable for more than 4 h. These results suggest that the alternative splicing of the RSU-1 RNA to produce the exon-deleted form constitutes a mechanism for reduction or loss of functional Rsu-1. Because the expression of Rsu-1 can inhibit malignant growth of glioblastoma cells, the depletion of Rsu-1, via the production of the alternatively spliced form of RSU-1, may inhibit growth regulation in tumors.
Chunduru
Suryaprabha
S
Department of Pathology and United States Military Cancer Institute, Uniformed Services University of the Health Sciences, Bethesda, MD 20814, USA.
Kawami
Hiroyuki
H
Gullick
Richard
R
Monacci
William J
WJ
Dougherty
Gerard
G
Cutler
Mary Lou
ML
D017398:Alternative Splicing; D000818:Animals; D019556:COS Cells; D002471:Cell Transformation, Neoplastic / Q000235:genetics; D004252:DNA Mutational Analysis; D005091:Exons / Q000235:genetics; D005784:Gene Amplification; D005910:Glioma / Q000235:genetics*; D006801:Humans; D016366:Open Reading Frames; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000235:genetics*; D014407:Tumor Cells, Cultured
D012333:RNA, Messenger; D014157:Transcription Factors; C076224:RSU1 protein, human