Differential expression and cellular localization of ZNF224 and ZNF255, two isoforms of the Krüppel-like zinc-finger protein family

We previously reported that ZNF224, a novel Krüppel-associated box-containing zinc-finger protein, represses aldolase A gene transcription by interacting with the KAP-1 co-repressor. Using northern blot and PCR procedures, we now demonstrate that the transcript encoding ZNF255 is a ZNF224 isoform and that the corresponding mRNAs are differentially expressed in human adult and foetal tissues. Moreover, transient transfection of recombinant ZNF224 and ZNF255 proteins and chromatin-immunoprecipitation assays indicate that ZNF224 binds the negative regulatory element of the aldolase A gene (AldA-NRE) and inhibits transcription more efficiently than ZNF255. Finally, ZNF224 was homogeneously distributed in the nucleus, whereas its isoform ZNF255 was identified in subnuclear structures in association with nucleoli, and also in the cytoplasm. The different repression of transcription and the different cellular localization of ZNF224 and ZNF255 suggest these proteins exert different biological role.