Can, a putative oncogene associated with myeloid leukemogenesis, may be activated by fusion of its 3' half to different genes: characterization of the set gene.

Abstract

The translocation (6;9)(p23;q34) in acute nonlymphocytic leukemia results in the formation of a highly consistent dek-can fusion gene. Translocation breakpoints invariably occur in single introns of dek and can, which were named icb-6 and icb-9, respectively. In a case of acute undifferentiated leukemia, a breakpoint was detected in icb-9 of can, whereas no breakpoint could be detected in dek. Genomic and cDNA cloning showed that instead of dek, a different gene was fused to can, which was named set. set encodes transcripts of 2.0 and 2.7 kb that result from the use of alternative polyadenylation sites. Translocations are the best-studied nonrandom chromosomal aberrations associated with specific subtypes of leukemia. As a result of a translocation, an oncogene can be activated through alterations in regulatory DNA sequences that leave the encoded protein intact (e.g., myc) or through formation of a fusion gene, encoding a chimeric protein (e.g., bcr-abl). The t(9;22) associated with chronic myeloid leukemia, acute myeloid leukemia (AML), and acute lymphoblastic leukemia (29) results in the expression of a chimeric BCR-ABL protein with enhanced tyrosine kinase activity (16,19,27,38,45). Pendergast et al. showed that defined sequences encoded by the first exon of bcr interact with the SH2 domain of ABL (33). This interaction is essential for the activation of the ABL tyrosine kinase activity and for the transforming capacity of BCR-ABL. More recently, other fusion genes have been isolated. t(1;19), occurring in childhood pre-B-cell acute leukemia, fuses the E2a gene, encoding transcription factors E12 and E47, to a novel homeobox gene, PBX1 (26, 32). t(15;17), strongly associated with acute promyelocytic leukemia, fuses part of the retinoic acid receptor type a gene (RARt) to a novel gene on chromosome 15 named PML, which is predicted to be a transcription factor (9, 25). bcr-abl, E2A-pbx, andpml-RARao seem to be highly consistent partners.Previously we reported the cloning of t(6;9) breakpoints (43). t(6;9) is the hallmark of a specific subtype of AML characterized by a poor prognosis and a young age of onset. It is classified in the French-American-British system mostly as M2/M4 and rarely as Ml or refractive anemia with excess of blast cells (RAEB) (2,36,39). On chromosome 9, break-* Corresponding author.points take place in a specific intron, icb-9, of a large gene (>140 kb) named Cain (can) (43). On chromosome 6, breakpoints also occur in a single intron, icb-6, of a gene named dek (42). The result of t(6;9) is the formation of a dek-can fusion gene on chromosome 6p-, which is transcribed into an invariable, 5.5-kb, leukemia-specific dek-can mRNA (39). The fusion transcript encodes a 165-kDa chimeric protein, which derives from the in-frame fusion of dek and can open reading frames (ORFs). Sequence comparison of DEK and CAN with entries in the EMBL data base shows no homology to any known protein sequences. CAN contains several putative dimerization motifs, and the C-terminal part may function as an ancillar...

HRX Leukemic Fusion Proteins Form a Heterocomplex with the Leukemia-associated Protein SET and Protein Phosphatase 2A

“…These two proteins have different amino termini of 37 amino acids (␣) and 24 amino acids (␤) but are otherwise identical throughout the other 253 amino acids of their sequences (43). Interestingly, the SET protein is a member of a chimeric fusion protein, SET-CAN, that arises as a result of chromosome translocations in acute undifferentiated leukemia (45). A nearly full-length SET protein is present in the SET-CAN fusion with only the last seven amino acids of SET lost upon translocation.…”

NAP‐I is a functional homologue of TAF‐I that is required for replication and transcription of the adenovirus genome in a chromatin‐like structure

“…Previous studies have shown that nucleosome assembly protein-I (NAP-I) has significant amino acid sequence similarity to TAF-I, and that it can substitute for TAF-I activity in the replication of Ad core DNA (von Lindern et al 1992a;Nagata et al 1995). Nucleosome assembly protein (NAP-I), which contains three negatively charged regions, is found in various eukaryotic cells and has been shown to interact with cellular histones and to facilitate nucleosome formation (Fujii-Nakata et al 1992;Ishimi et al 1987).…”

“…TAF-Ib corresponds to the protein encoded by the set gene. The set-can fusion gene derived from chromosomal translocation is thought to be a putative oncogene associated with acute undifferentiated leukaemia (von Lindern et al 1992a). The expression of SET/TAF-Ib is ubiquitous in a variety of cells.…”

“…However, the functions of SET/TAF-Ib, CAN and SET/TAF-Ib-CAN are not clear. TAF-I shows significant homology with nucleosome assembly protein-I (NAP-I) von Lindern et al 1992a), which contains tripartite negatively charged regions (Fujii-Nakata et al 1992;Ishimi & Kikuchi 1991). NAP-I transfers histones to DNA and facilitates the association of histones with DNA to form nucleosomes (Ishimi et al 1987).…”

Glyceraldehyde 3-phosphate dehydrogenase is a SET-binding protein and regulates cyclin B-cdk1 activity

“…In addition to the association with cyclin-cdks, p21 Cip1 also interacts with a growing number of proteins, indicating that it is involved in the regulation of many other cellular functions (Coqueret, 2003). We have previously reported that p21 Cip1 interacts with the SET protein, which was firstly identified as a CAN-fusion gene in an acute undifferentiated leukemia (von Lindern et al, 1992;Adachi et al, 1994). SET belongs to a family of proteins, which includes the yeast nucleosome assembly protein NAP-I (Kawase et al, 1996), MB20 (Shen et al, 2001), Cell Division Antigen-1 (Chai et al, 2001), nucleolar transforming growth factor-b1 target (Ozbun et al, 2001), supressor of presenilin-2 (Wen et al, 2000) and testis-specific protein Y-encoded (Vogel et al, 1998).…”