Enhanced stability of interleukin-2 mRNA in MLA 144 cells. Possible role of cytoplasmic AU-rich sequence-binding proteins.
The MLA 144 gibbon T cell line is infected with a type C retrovirus and constitutively expresses interleukin-2 (IL-2) and granulocyte macrophage colony-stimulating factor (GM-CSF). IL-2 mRNA levels are 10-fold more abundant than GM-CSF in these cells. Comparable transcriptional rates for these lymphokines suggested the involvement of post-transcriptional mechanisms in selective IL-2 mRNA accumulation. IL-2 mRNA is exceptionally stable in MLA cells with a t1/2 of more than 8 h. The presence of reiterated AUUUA sequences in the 3'-untranslated region (UTR) has been shown to confer mRNA lability. The provirally altered MLA IL-2 allele encodes an mRNA in which three AUUUA motifs have been deleted. Six major cytoplasmic proteins bound in vitro transcribed RNA probes containing sequences from the 3'-UTR of normal human IL-2 (3'-IL-2), GM-CSF (delta 2R1), and the virally altered MLA IL-2 (3'-IL-2 PV) mRNA. Increased binding of these proteins to 3'-IL-2 PV was observed relative to 3'-IL-2 or delta 2R1. Northwestern blotting demonstrated similar differential ability of a 36- and 43-kDa protein to bind, as well as showed that these proteins colocalized by immunoblotting as hnRNP A1 and C, respectively. These findings suggest a direct correlation between differential binding of cytoplasmic proteins to AU-rich 3'-UTRs in vitro and lymphokine mRNA stability in vivo.
Henics
T
T
Veterans Administration Medical Center, Research Laboratories, White River Junction, Vermont 05009.
Sanfridson
A
A
Hamilton
B J
BJ
Nagy
E
E
Rigby
W F
WF
D000483:Alleles; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D003609:Dactinomycin / Q000494:pharmacology; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000096:biosynthesis / Q000235:genetics; D006801:Humans; D006922:Hylobates; D007376:Interleukin-2 / Q000096:biosynthesis* / Q000235:genetics; D008969:Molecular Sequence Data; D015347:RNA Probes; D012323:RNA Processing, Post-Transcriptional; D012333:RNA, Messenger / Q000737:chemistry / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism*; D012091:Repetitive Sequences, Nucleic Acid; D013379:Substrate Specificity; D013601:T-Lymphocytes / Q000276:immunology; D014158:Transcription, Genetic / Q000187:drug effects
D007376:Interleukin-2; D015347:RNA Probes; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D003609:Dactinomycin; D016178:Granulocyte-Macrophage Colony-Stimulating Factor