Distribution of Fhit protein in rat tissues and its intracellular localization

The FHIT (fragile histidine triad) gene located at chromosome 3p14.2 has be en proposed as a candidate tumor suppressor gene in human cancers. Fhit pro tein with the diadenosine 5',5'"-P-1,P-3-triphosphate (Ap(3)A) hydrolase ac tivity is the protein product of FHIT gene. The way in which Fhit exerts it s tumor suppressor activity and the relationship of the Ap(3)A hydrolase ac tivity to tumor suppression are not known. As a step toward understanding o f the Fhit function in the cell we have explored its intracellular localiza tion and distribution in the rat tissues. Data obtained from immunoblot ana lysis showed that Fhit protein was most abundant in spleen and brain. Moder ate amount of Fhit was detected in kidney and liver, whereas the level of F hit protein in heart, skeletal muscle and kidney glomeruli was undetectable . RT-PCR performed on RNA isolated from these tissues showed no product, wh ereas the level of Fhit mRNA in spleen, brain, kidney, liver and lung corre lated with the Fhit protein level. The immunoblot analysis performed on sub cellular fractions of various rat tissues obtained by differential and dens ity-gradient centrifugation showed that Fhit protein was localized exclusiv ely in nucleus and at the plasma membrane. Presented data showing nuclear a nd plasma membrane localization of Fhit may support the hypothesis concerni ng Fhit as a signaling molecule.