Comparison of two promoters controlling expression of secreted or intracellular IL-1 receptor antagonist.
IL-1R antagonist can be expressed as a secreted glycoprotein (sIL-1Ra) or as an intracellular nonglycosylated form (icIL-1Ra). The two isoforms only differ in their N-terminal sequences and are thought to originate, by selection of alternative first exons, from a single gene (IL-1RN). We have previously described a clone that encodes the exons and promoter for sIL-1Ra. In this work, we describe and characterize a clone that contains the further upstream, alternative first exon used to generate icIL-1Ra. Sequences upstream to this alternative exon are demonstrated to have promoter activity in the human colon epithelial cell line HT29, whereas the sIL-1Ra promoter has undetectable activity. Both the icIL-1Ra and sIL-1Ra promoters were active when transfected into THP-1 cells. Neither promoter was responsive to PMA or LPS when introduced into HT29 or THP-1 cells. Activity of the endogenous icIL-1Ra and sIL-1Ra promoters was also investigated. In agreement with the transfected icIL-1Ra promoter, the endogenous icIL-1Ra gene is active in HT29 cells, though induced by PMA. In contrast to the transfected icIL-1Ra promoter, the endogenous icIL-1Ra gene is inactive in THP-1 cells and induced by PMA. Our data complete the structure of the human IL-1RN gene, demonstrating that the two forms of IL-1Ra are produced from the same gene by use of alternative first exons. We also show that there are two distinct promoters that control IL-1Ra expression, that lie upstream to each alternative first exon.
Butcher
C
C
Yamanouchi Research Institute U.K. Littlemore Hospital, Oxford, England.
Steinkasserer
A
A
Tejura
S
S
Lennard
A C
AC
D001483:Base Sequence; D002460:Cell Line; D003001:Cloning, Molecular; D005786:Gene Expression Regulation; D006801:Humans; D053590:Interleukin 1 Receptor Antagonist Protein; D008070:Lipopolysaccharides / Q000494:pharmacology; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D017472:Receptors, Interleukin-1 / Q000037:antagonists & inhibitors*; D012795:Sialoglycoproteins / Q000235:genetics* / Q000502:physiology; D014158:Transcription, Genetic
C507763:IL1RN protein, human; D053590:Interleukin 1 Receptor Antagonist Protein; D008070:Lipopolysaccharides; D017472:Receptors, Interleukin-1; D012795:Sialoglycoproteins