The human L-myc gene encodes multiple nuclear phosphoproteins from alternatively processed mRNAs.
The human proto-oncogene L-myc generates at least four different mRNAs by alternative RNA processing. We have identified two phosphorylated L-myc proteins with molecular masses of 60,000 and 66,000 daltons [p60L-myc(human) and p66L-myc(human)] in a small-cell carcinoma line expressing high levels of L-myc mRNA. These proteins have a short half-life and are localized to the nuclear matrix fraction, as previously reported for the c-myc and N-myc proteins. In vitro translation experiments demonstrated that both the p60 and p66 species are encoded by a 3.9-kilobase (kb) mRNA which retains intron 1, while only the p60 protein is translated from a 3.6-kb L-myc mRNA which has had intron 1 removed. While L-myc proteins [p32L-myc(human) and p37L-myc(human)] could be synthesized in vitro from 2.2-kb mRNA templates, no such proteins were detected by immunoprecipitation in vivo. These observations suggest that alternative RNA processing of the L-myc transcript could play a role in determining the steady-state levels of the p60L-myc and p66L-myc proteins.
De Greve
J
J
National Cancer Institute and Naval Hospital, Bethesda, Maryland 20814.
Battey
J
J
Fedorko
J
J
Birrer
M
M
Evan
G
G
Kaye
F
F
Sausville
E
E
Minna
J
J
D006801:Humans; D008970:Molecular Weight; D009687:Nuclear Proteins / Q000235:genetics*; D009857:Oncogenes; D010750:Phosphoproteins / Q000235:genetics*; D011233:Precipitin Tests; D014176:Protein Biosynthesis; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000276:immunology; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics* / Q000276:immunology; D011519:Proto-Oncogenes; D012326:RNA Splicing; D012333:RNA, Messenger / Q000235:genetics*; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured
C000715470:MAS1 protein, human; C000596782:MYCL protein, human; D009687:Nuclear Proteins; D010750:Phosphoproteins; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger