Identification of a novel Ran binding protein 2 related gene (RANBP2L1) and detection of a gene cluster on human chromosome 2q11-q12.

The giant 358-kDa protein Ran binding protein 2 (RanBP2/Nup358) is localized at the cytoplasmic side of the nuclear pore complex and likely constitutes the Ran-GTP binding site at the cytoplasmic face of the complex. RanBP2/Nup358 furthermore acts as a chaperone for red/green opsin molecules. Here, we report on the physical mapping of human RanBP2 between markers D2S340 and D2S1893. A duplication of the 5'-end sequence of RanBP2 occurs within 3 Mb distal to RanBP2. Detailed sequence analysis resulted in primers specific for this distal duplication. Polymerase chain reaction-based screening of cDNA libraries indicates that this transcript, called RanBP2alpha (HGMW-approved symbol RANBP2L1), is expressed in several tissues. Screening of a fetal brain cDNA library yielded a 4057-bp partial cDNA clone for RanBP2alpha. Its 5'-end is almost identical to RanBP2, whereas its 3'-part is distinct from RanBP2. Northern blot analysis using a probe of the 3'-untranslated sequence of RanBP2alpha detected in several tissues an 8-kb transcript representing the full length of the transcript. In pancreas and placenta, an additional transcript of 14 kb was detected. PAC clones containing the bona fide RanBP2 sequences were localized to 2q11-q12 by FISH analysis, and a region of high similarity was detected on 2p11-p12. In summary, we have identified a RanBP2 gene cluster on 2q11-q12 together with a novel gene termed RanBP2alpha, with high sequence similarity to RanBP2.