A splicing enhancer in the 3'-terminal c-H-ras exon influences mRNA abundance and transforming activity.
Analysis of cDNA clones previously identified an optional intron in the 3'-untranslated region of the human H-ras gene. A possible correlation was observed between failure to remove this intron and overexpression of the gene, suggesting that splicing of the intron may require a specific titrable factor. The splicing signals at the end of the intron deviate from the consensus and may be inefficient, but we noticed that the adjacent exon downstream has a purine-rich region reminiscent of purine-rich splicing enhancers in other genes that stimulate the removal of weak, flanking introns. We show here that the purine-rich region of H-ras has splicing-enhancer activity in the homologous as well as a heterologous context. Interestingly, although the affected intron is outside the coding region, inversion or deletion of the enhancer reduced the transforming activity of oncogenic H-ras alleles severalfold. Experiments with corresponding cDNA constructs suggested that this is not a consequence of the altered structures of the mRNAs produced when the enhancer is inverted or deleted. Instead, we propose that the region controls an additional pre-mRNA processing event besides splicing of the terminal intron. Our work indicates that the purine-rich region may play an important role in the control of H-ras activity.
Hwang
D Y
DY
Department of Molecular Genetics and Biochemistry, School of Medicine, University of Pittsburgh, Pennsylvania 15261, USA.
Cohen
J B
JB
D000818:Animals; D001483:Base Sequence; D007446:Chromosome Inversion; D004247:DNA; D004742:Enhancer Elements, Genetic; D005091:Exons; D015870:Gene Expression; D006801:Humans; D008969:Molecular Sequence Data; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics*; D011687:Purines; D012326:RNA Splicing; D012333:RNA, Messenger / Q000378:metabolism*; D017384:Sequence Deletion; D014170:Transformation, Genetic
D011687:Purines; D012333:RNA, Messenger; D004247:DNA; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras); C030985:purine