The leukemia-associated-protein (LAP) domain, a cysteine-rich motif, is present in a wide range of proteins, including MLL, AF10, and MLLT6 proteins.

Abstract

We have identified and further characterized a Caenorhabditis elegans gene, CEZF, that encodes a protein with substantial homology to the zinc rmger and leucine zipper motifs of the human gene products AF10, MLLT6, and BR140. The first part of the zinc finger region of CEZF has strong similarity to the corresponding regions of AF10 (66%) and MLLT6 (64%) at the cDNA level. As this region is structurally different from previously described zinc finger motifs, sequence homology searches were done. Twenty-five other proteins with a similar motif were identified. Because the functional domain of this motif is potentially disrupted in leukemia-associated chromosomal translocations, we propose the name of leukemia-associated protein (LAP) finger. On the basis of these comparisons, the LAP domain consensus sequence is Cys'-Xaal-2-Cys2-Xaa,_21-Cys3-Xaa2-4-Cys4-Xaa4_5-His5-Xaa2-Cys6-Xaa2_46_-Cys7-Xaa2-Cys8, where subscripted numbers represent the number of amino acid residues. We review the evidence that this motif binds zinc, is the important DNA-binding domain in this group of regulatory proteins, and may be involved in leukemogenesis.The predicted product of the gene AFJO on. chromosome 10p12, involved in the translocation t(10;11)(pl2;q23) seen in acute myeloid leukemias (1), has a potential zinc finger domain at the N terminus and a leucine zipper near the C-terminal end. Homology exists at the protein level in the zinc finger and leucine zipper regions of AF10 with two previously described human DNA sequences: an MLL partner gene MLLT6 on chromosome 17q21 (2) and BR140 for which function and chromosomal location are unknown (3), and a putative Caenorhabditis elegans gene that we have named CEZF (1).t Although the zinc finger domains are conserved in these four genes, they do not show characteristics common to any of the previously described zinc-binding motifs described so far. There are at least six different families of cysteine-rich proteins identified to have zinc-binding domains (4). Of these the RING (5), LIM (6), and Kruppel (7) fingers have been involved in chromosomal translocations in acute leukemia. In this paper we further characterize CEZF and the conserved zinc finger domain. We report the identification of another class of zinc finger proteins involved in a wide range of proteins, including leukemia-associated fusion proteins. MATERIALS AND METHODSNucleic Acid Analysis. The partially sequenced C. elegans cDNA clone yK46c2 has been reported (1) to have homology with AF10. It is 3.2 kb in size, obtained from an oligo(dT)-primed A ZAP (Stratagene) C. elegans cDNA library, and maps to chromosome III (8). Complete sequencing of clone yK46c2 on both strands was done in an Applied Biosystem automatic sequencer using the Prism ready reaction dideoxy termination cycle sequencing kit (Applied Biosystems).DNA Alignment. Exon-intron boundaries were mapped by comparing the cDNA sequence with the C. elegans genomic sequence from cosmid F54F2.2 available in the data base (accession no. L23645) (8).Multiple P...

The cloning, mapping and expression of a novel gene, BRL, related to the AF10 leukaemia gene

“…The ®rst 46 amino acids of the CRR contain a LAP/PHD motif, a feature which has been found in a wide variety of proteins and has been described in detail elsewhere (Saha et al, 1995). There are currently little experimental data on the functional role of the LAP/PHD domain.…”

“…The exceptions to this include one adult case of acute myeloid leukaemia demonstrating a t(10;11) translocation (Chaplin et al, 1995a,b) and also the t(10;11) translocation of U937 cell line (Dreyling et al, 1996), in both of which the breaks in AF10 occur within the CRR. It is possible that the cysteine rich regions are important to the transcriptional regulation of myeloid cells (Saha et al, 1995) and that their loss or disruption is critical to malignant transformation in haematopoietic cells.…”

“…This region also has signi®cant homology to the equivalent cysteine rich domains in AF10, AF17 and CEZF. The CRR can be considered in two parts: the ®rst 46 amino acids can be con®gured as a LAP or PHD motif, a feature which has been identi®ed in a wide range of proteins from di erent species where it is found as a single or repeated domain (Saha et al, 1995). The remaining carboxy part of the CRR in BRL is homologous to similar regions in AF10, AF17 and BR140.…”

“…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.…”

MOZ and MORF, two large MYSTic HATs in normal and cancer stem cells

“…PHD fingers are present in many chromatin regulators (Saha et al, 1995). As PHD fingers have the potential to bind phosphoinositides and are implicated in nuclear lipid signaling (Gozani et al, 2003), an interesting possibility is that phosphoinositides bind directly to MOZ and MORF complexes and regulate their activity.…”