MULTIPLE METHYLATION-FREE ISLANDS FLANK A SMALL BREAKPOINT CLUSTER REGION ON 11P13 IN THE T(11-14)(P13-Q11) TRANSLOCATION

The t(11;14)(p13;q11) translocation is one of the most frequent chromosomal abnormalities in T‐cell acute lymphoblastic leukemia (ALL). Ten different leukemias carrying this translocation have been analysed and all 10 breakpoints fall within a region of less than 25 kb on chromosome band 11p13. We have used PFGE and cosmid cloning to assess the presence of potential genes by analysing methylation‐free islands in the vicinity. Four methylation‐free islands, within 270 kb, flank the t(11;14)‐associated breakpoint cluster region (T‐ALLbcr), one occurring about 25 kb on the telomeric side and one about 100 kb on the centromeric side of the T‐ALLbcr. Evidence for eight further methylation‐free islands on both sides of the T‐ALLbcr region is also presented. Thus multiple methylation‐free islands exist on 11p13 flanking the t(11;14)(p13;q11) translocation‐associated breakpoint cluster region, representing multiple potential transcription units whose chromosomal environment is altered by chromosome translocation. Copyright © 1990 Wiley‐Liss, Inc., A Wiley Company