Increased expression of 5q31 fragile site in a Bloom syndrome family.

In this work, we report spontaneous chromosomal breakpoints and fragile site expression induced by 5-fluorodeoxyuridine (FdUrd) and FdUrd plus caffeine in a family with Bloom's syndrome (BS) and 2 healthy donors. Standard and G-banded metaphases from each individual and each treatment were analyzed. Among the 59 common fragile sites (c-fra) identified in this work, only the frequency of 5q31 was significantly increased in the BS family with respect to healthy donors (P less than 0.005). A remarkable coincidence between the breakpoints involved in spontaneous chromosome aberrations and induced c-fra was found in BS homozygote patients. The importance of the interaction between fragile sites and chromosome rearrangements in cancer is discussed.