PREFERENTIAL EXPRESSION OF HMGI-C ISOFORMS LACKING THE ACIDIC CARBOXY-TERMINAL IN HUMAN LEUKEMIA

The high mobility group HMGI chromasomal proteins are an important com ponent of chromatin. The HMGI-C protein consists of three amino termin al DNA binding domains (''AT hooks''), a linker region and an acidic c arboxy domain. In mesenchymal tumors, chromosomal translocations of 12 q13-15 result in fusion proteins containing the AT hooks and novel car boxy terminals. We have investigated the status of the HMGI-C gene in two eases of leukemia with anomalies of chromosome 12q and identified three novel isoforms (designated alpha, beta and gamma) derived from a lternate splicing. One of the patients expressed all three isoforms, w hereas the second patient expressed only the gamma isoform; preferenti al expression of the HMGI-C gamma isoform was also detected in the leu kemic cell lines ML3 and BV173. The results are consistent with a cruc ial role for truncation of the acidic carboxy domain of HMGI-C in abno rmal growth. (C) 1998 Academic Press.