Evidence for a new transcript of the Epstein-Barr virus C3d receptor (CR2,CD21) which is due to alternative exon usage

CR2 extracellular domain is constituted of 15 or 16 Short Consensus Repeats (SCR), with additional SCR 11 localized between SCRs 10 and 12. We amplifi ed Raji cDNA library, with specific primers where SCR 11 is localized. This generated a new fragment of 643 bp (16b SCR), in addition to the two expec ted transcripts of 489 (15 SCR) and 667 (Iba SCR) bp. Sequencing these thre e fragments and the corresponding genomic DNA, demonstrated the presence of a 24 bp deletion in 16b SCR, without change of open reading frame and that this 24 bp region was flanked by two splicing acceptor sites. This support ed a new alternative splicing of CR2, with generation of a third distinct m RNA. This third transcript was expressed in human CR2 positive T cells. nor mal or transformed B cells and EBV negative B cell lines. The 24 bp deletio n corresponds to a proline-rich region, which may influence CR2 conformatio n and more likely have consequences on CR2 extra and intracellular interact ions. (C) 1999 Elsevier Science Ltd. All rights reserved.