ANALYSIS OF THE GENE THAT ENCODES THE COMPLEMENT REGULATORY PROTEIN, MEMBRANE INHIBITOR OF REACTIVE LYSIS (CD59) - IDENTIFICATION OF AN ALTERNATIVELY SPLICED EXON AND CHARACTERIZATION OF THE TRANSCRIPTIONAL REGULATORY REGIONS OF THE PROMOTER

Membrane inhibitor of reactive lysis (MIRL, CD59) is an 18-kDa glycosy lphosphatidylinositol-anchored protein that regulates formation of the membrane attack complex of complement. The purpose of these studies w as to characterize the gene that encodes CD59. Our experiments redefin ed the structural organization of the gene by identifying a previously unrecognized alternatively spliced exon. Analysis by PCR of cDNA deri ved from a variety oi cultured human cell lines and from PBMC showed t hat transcripts containing the alternatively spliced exon sequence wer e expressed concordantly with transcripts lacking that sequence. Prime r extension studies demonstrated that the transcriptional start site o f alternatively spliced CD59 mRNA is the same as that of transcripts w ithout the alternatively spliced exon sequence, suggesting that expres sion of both forms of CD59 mRNA is regulated similarly. Analysis of th e promoter region showed that the first 70 nucleotides immediately 5' of the transcriptional start site of the CD59 gene are essential for b oth constitutive and PMA-responsive transcription; however, responsive ness to PMA is cell line specific. Together, these studies have redefi ned the organization of the CD59 gene and identified regions of the pr omoter involved in constitutive and PMA-inducible transcription.