BCMSUN, a candidate gene for B-cell chronic lymphocytic leukemia and mantle-cell lymphoma, has an independently expressed homolog on 1p22-p31, BCMSUN-like

The most frequent chromosomal imbalance in B-cell chronic lymphocytic leuke mia (B-CLL) and mantle cell lymphoma (MCL) is loss of material from 13q14.3 . BCMSUN (previously Leu2, t4, cDNA IB4) is one of 3 proposed candidate gen es isolated from the minimally deleted region. We identified a homolog of B CMSUN, termed BCMSUNL (for BCMSUN-like). Radiation-hybrid mapping with a PC R-amplifled fragment and fluorescence in site hybridization with 2 PAC clon es containing coding information for BCMSUNL revealed its localization at I p22-p3 I. Interphase fluorescence in situ hybridization, however, revealed that the BCMSUNL gene locus is not part of the critical deletion region of I p22 in MCLs. Analysis of DNA sequences derived from the respective PAC c lones and available in public databases uncovered an intronless structure o f BCMSUNL. Compared to BCMSUN, the new gene lacks exon 2 and shows 90.3% ho mology on the nucleic acid level. Both genes are expressed in peripheral bl ood lymphocytes from healthy donors as well as B-CLL and MCL tumors, with r etention of genetic material at 13q14.3. Therefore, analysis of the candida te tumor-suppressor gene BCMSUN at 13q14.3 must be based on assays that dis tinguish between the 2 homologous genes. (C) 2000 Wiley-Liss, Inc.