The cloning, mapping and expression of a novel gene, BRL, related to the AF10 leukaemia gene Paul McCullagh 1 , Tracy Chaplin 1 , Joanne Meerabux 1 , Demetrios Grenzelias 1 , Debra Lillington 1 , Richard Poulsom 2 , Armando Gregorini 1 , Vaskar Saha 1 and Bryan D Young* ,1 1 Imperial Cancer Research Fund, Department of Medical Oncology, St Bartholomew's and the Royal London School of Medicine and Dentistry, Charterhouse Square, London ECIM 6BQ, UK; 2 In Situ Hybridization Service, Imperial Cancer Research Fund, 44 Lincoln's Inn Fields, London WC2A 3PX UK The MLL gene is reciprocally translocated with one of a number of dierent partner genes in a proportion of human acute leukaemias. The precise mechanism of oncogenic transformation is unclear since most of the partner genes encode unrelated proteins. However, two partner genes, AF10 and AF17 are related through the presence of a cysteine rich region and a leucine zipper. The identi®cation of other proteins with these structures will aid our understanding of their role in normal and leukaemic cells. We report the cloning of a novel human gene (BRL) which encodes a protein containing a cysteine rich region related to that of AF10 and AF17 and is overall most closely related to the previously known protein BR140. BRL maps to chromosome 22q13 and shows high levels of expression in testis and several cell lines. The deduced protein sequence also contains a bromodomain, four potential LXXLL motifs and four predicted nuclear localization signals. A monoclonal antibody raised to a BRL peptide sequence con®rmed its widespread expression as a 120 Kd protein and demonstrated localization to the nucleus within sperma- tocytes. Keywords: chromosome translocation; leukaemia; MLL; AF10 Introduction The analysis of chromosomal translocations aecting chromosome 11 at band q23 in leukaemias has shown that these events involve fusions between the human trithorax (MLL) gene (Djabali et al., 1992; Gu et al., 1992; Tkachuk et al., 1992; Ziemin-van der Poel et al., 1991) and a variety of partner genes (Bernard and Berger, 1995) each providing a COOH region to the resultant fusion protein. These translocations result in in-frame fusions suggesting an important role for the dierent COOH regions in the oncogenic transforma- tion. This is supported by the demonstration that a germline fusion between MLL and AF9, created by homologous recombination, results in leukaemias in chimeric mice (Corral et al., 1996). The t(10;11)(p12;q23) translocation which occurs in acute myeloid leukaemia (AML) has been shown to result in fusion of the 3' portion of the AF10 gene to the 5' portion of the MLL gene (Chaplin et al., 1995a). The AF10 gene encodes a protein with two identi®able features, a cysteine rich region (CRR) at its amino terminus and a putative leucine zipper sequence towards the carboxy terminus. It is now clear that the MLL-AF10 fusion is rather unusual in that the MLL and AF10 genes lie in opposite orientations with respect to the chromosomal telomeres (Beverloo et al., 1995). Inversion of one of the genes has to occur in order to achieve a stable fusion, thus accounting for the inversion and insertion of parts of the long arm of chromosome 11 into the short arm of chromosome 10 noted in previous cytogenetic studies (Le Beau et al., 1985). Despite the complexity of the AF10 transloca- tions a consistent feature seems to be the fusion of the leucine zipper domain to MLL (Chaplin et al., 1995b). Another important feature of AF10, so far unusual for MLL partner genes, is that it has been found rearranged with genes other than MLL, namely CALM, in the U937 cell line (Dreyling et al., 1996) and HEAB in an invins(10;11)(p12;q23q12) in a 2 year old child with acute monoblastic leukaemia (Tanabe et al., 1996). AF17, the gene involved in the t(11;17) translocation (Prasad et al., 1994) encodes a protein containing a cysteine rich region and a potential leucine zipper domain, both highly homologous with the same features in AF10. The breakpoints within AF17 also occur between the CRR and the leucine zipper, and similarly result in the fusion of the 3' end of the AF17 gene with the 5' end of the MLL gene. The ®rst part of the CRR in AF10 and AF17 consists of a C4HC3 conserved putative zinc ®nger motif known as the LAP domain (Saha et al., 1995), PHD ®nger (Aasland et al., 1995) or TTC domain (Koken et al., 1995). The remainder of the CRR in AF10 and AF17 (116 amino acids) contains a cluster of 12 conserved cysteines and histidines. A similar CRR structure has been identi®ed in a protein of unknown function encoded by the gene BR140 (Thompson et al., 1994). Interestingly, the MLL protein also contains the elements found in this CRR, i.e. LAP/PHD with a similar cluster of 12 cysteines and histidines located 250 residues down- stream. An important observation is that in the translocations so far described, the CRR regions of MLL, AF10 and AF17 are either lost or disrupted following translocation, suggesting an important oncogenic role for this region. We describe the cloning, chromosomal mapping and expression of a new human gene designated BRL (BR140 Like gene) which encodes a protein with a CRR related to similar structures in MLL, AF10, AF17 and BR140. *Correspondence: BD Young Received 4 June 1999; revised 29 July 1999; accepted 5 August 1999 Oncogene (1999) 18, 7442 ± 7452 ã 1999 Stockton Press All rights reserved 0950 ± 9232/99 $15.00 http://www.stockton-press.co.uk/onc