A YEAST ARTIFICIAL CHROMOSOME CONTIG THAT SPANS THE RB1-D13S31 INTERVAL ON HUMAN-CHROMOSOME-13 AND ENCOMPASSES THE FREQUENTLY DELETED REGION IN B-CELL CHRONIC LYMPHOCYTIC-LEUKEMIA

Abnormalities involving chromosome 13 have been reported as the only c ytogenetic change in B-cell chronic lymphocytic leukemia (BCLL). Delet ions are the most common cytogenetic abnormality and always involve 13 q14, but when translocations are seen, the consistent breakpoint is al ways in 13q14. It is now established that deletions, distal to the RB1 gene in 13q14, are invariably associated with these translocations. W e have recently described the smallest such deletion from a series of rearrangements from these tumors isolated in somatic cell hybrids, whi ch spans approximately 1 Mb. In this report, we present the results of a series of a chromosome walking experiments using YACs and have been able to span this small deletion, which must contain the gene that is frequently deleted in BCLL. Four probes from 13q14 (RB1-mgg15-D13S25- D13S31) were used to isolate corresponding YACs for each of the marker s. The chromosomal location of these YACs was verified using FISH, whi ch also demonstrated their nonchimeric nature. Vectorette end rescue w as then used to demonstrate the overlap of the YACs and to isolate new clones to complete the contig. The extremes of the contig were shown to cross the chromosome 13 translocation breakpoints isolated in somat ic cell hybrids that carry the derivatives of chromosome 13 involved i n the smallest BCLL deletion. This YAC contig covers the entire deleti on and will prove a valuable resource to begin isolating genes from th is region, In addition, we have isolated YACs corresponding to the RBI locus, which extends the contig over a 3.8-cM distance on the chromos ome. (C) 1995 Academic Press, Inc.